Engineering Rome


Table of Contents



When I was a kid I would got to church with my families. All of the churches I went to had a basilica style church. I did not know it was a basilica at the time but the building structure was almost a definition of what Catholicism is. When someone mentions Christianity, I think of the grand building with high arches, light entering from the top and the whole building seeming to point to the focal point at the back of the church. This building style gives the look and feel to what Christianity is. It was not always that way however. The basilica form was first invented by ancient Rome. The structure was then used by Christianity and gained another religious definition. The building structure, which was an architectural masterpiece in ancient Rome, has changed over time with many variations. Even through the long passing of time, it still has a strong impact on the world today.

Ancient Rome was a public city. The Baths of Caracalla was a public place where people could relax and converse with each other. The Coliseum was a giant theatre provided for the public to enjoy. Ancient Rome even had a senate. They needed a public building where they could conduct business and or settle any legal matters. The basilica was created to take care of these concerns.

The Latin word of basilica was derived from the Greek “Basilike stoa” where “basilike” means kingly or royalty that defines the noun “stoa”, an open aired portico. The term basilica refers to a building that works as a meeting hall. The basilica structure is great for this purpose. Using large columns and arches you can feel the enormity of the structure that can allow thousands of people into the building at once. At the same time, its rectangular shape allows a focal point in the building at one end or the other. Together this allows a large amount to people to focus on one unified goal.

In ancient Rome these basilicas were created in the Roman Forum, the center of the ancient city. They were in essence an extension of the Roman Forum that was used when something needed to be done indoors. It can be considered a covered forum. These building would usually be named after the person who paid for their construction. This was done to help cement that person’s status and legacy. Some of the remains of these basilicas can still be seen in Roman Forum. Although one is not able to see the complete building, the remains of the columns and the layout of some of these structures can still be seen today.

There were four basilicas created in the Roman Forum in the period of the Roman Republic. The first basilica built in Rome was the Basilica Porcia. Founded by Marcus Portius Cato in 184 BC. It started the process of monumentalizing the Roman Forum in the Roman Republic time. Unfortunately, fires were common in the ancient city and one fire in 52 BC burned down the city. It was not rebuilt. The other basilicas created in the era were the Basilica Aemelia, created in 179 BC, Basilica Sempronia, 169 BC, and the Basilica Opimia, 121 BC. The basilicas Sempronia and Opimia were torn down to create the Basilica Julia and theTemple of Concord respectively. Only the Basilica Aemelia has remains left in the Roman Forum. More basilicas were built after the Roman Republic during the Roman Empire. Julies Cesar replaced the Basilica Sempronia to create a much larger and grander Basilica Julia. It was created around 54-48 BC. Although Julies Cesar started the project, Augustus Cesar finished it after his great uncle got assassinated. It was created for official roman meeting and held the Centumviral Court, 180 jurors who heard civil lawsuits. The last basilica created in the Roman Forum was the Basilica Maxentius or the Basilica of Constantine. Started by emperor Maxentii, it was finished by Constantine following the defeat of Maxentii at the Battle of Mulvian Bridge. Constantine altered the original plans of the building to his liking.

The Roman Forum: In this map you can see the Basilica Fulvia, Basilica Julia and Basilica Maxentius or Constantine

Once Constantine defeated Maxentii at the Battle of Mulvian Bridge started a turning point to the use of basilicas. The Roman Empire started to crumble and traditional basilicas were not created any more. Constantine converted to Christianity. Rome, which once believed in multiple gods and had different temples honoring each one, became a catholic city. Catholicism was able to spread into Europe and later over the world. Before the wide spread acceptance of Catholicism in Rome Christians used to celebrate their religion using their own houses and small cave dwellings in hiding. Since they were not being persecuted any longer they were able to create much more grand monuments and places of worship. Christians had to choose a usable model to create these places of worship. They were not able to use Roman temples due to their relationship to past pagan religions and the fact that these buildings would not be able to hold large amounts of people for worship. They were designed to hold an image, not to hold a congregation. The default choice ended up being the basilica form.

The basilicas used for the church were different than the ones used in the Roman Forum. Variations were made in these buildings due to their different function compared to classical basilicas. Instead of strictly a place of business, Christian basilicas were used as a place of worship and people had different needs for these buildings. The interiors of these buildings were changed so that the clergy could officiate easier. Emperor Constantine was the person that introduced transepts to these basilicas to make them into a cross shape. This resemblance to the cross that Jesus Christ died on made basilicas extremely popular for Christian churches.

With the popularity of basilicas in the Roman Church, the definition of the word basilica itself changed due to its close association with the church. This can cause a lot of confusion in what a basilica is. If you look at the definition of basilica, it gives you two meanings. One definition is architectural referring to the building that is rectangular in shape and used in ancient Rome. The other definition is religious. The Catholic Church can deem any church a basilica if the church is deemed to have religious importance. There are even distinction in the types of basilicas with major basilicas and minor basilicas. This can make it extremely complicated in naming a church a basilica. A church can be called a basilica by the Catholic Church but not be a basilica in the architectural definition. St. Peters Basilica, a major basilica, is not necessarily a basilica in the architectural sense. However all of the other major basilicas are basilicas in the architectural sense. On the other side, ancient roman basilicas were not basilicas in the religious definition because they were not churches and did not have any religious importance. This article will go into the churches that are basilicas in the architectural sense. While this article will not go into the religious basilicas and their importance, it does show the strong connection between the basilica form and the Roman Church.

What can add more confusion is that a basilica form building is also a flexible definition. There are some buildings that are obviously basilicas in the architectural sense by looking at its form. This includes all of the ancient roman basilicas. There are other buildings however that has parts of it that resemble a basilica but have such great variations that it is hard to call it a basilica. One great example is St. Peters Basilica. Although it is a basilica in the religious sense, the original plan was of a centrally planned church. It ended up having basilica components inside the church but it is still hard to consider it a true basilica.

So what is a basilica in the architectural sense? A basilica is a large building that has a rectangular form. It usually has two sets of colonnades, sets of evenly spaced pillars used to support the building. These colonnades are arranged going with the length of the building that creates three different aisles in the building. The middle one is called the nave that usually has a much larger ceiling than the two side aisles. Some basilicas, like the Basilica Ulpia, have more than two side aisles by having more than two sets of colonnades. On one or multiple side of the building they would have an apse. An apse is a semi-circular dome one side of the building. In churches, the apse would act as the focal point of the building where the clergy would do their rituals for Christianity. In the central nave they would have windows on the side since the central roof is taller than the side roofs. This top area is called the clerestory. These building would usually have a room on one side of the building. In ancient Rome they would be called vestibule while in churches they would be called a narthex.

Components of a basilica style churh

There were many differences in the design of an ancient roman basilica compared to a church basilica. While the entrance to an ancient roman basilica would be on the longer side of the building, the entrance to a religious basilica would be on one of the shorter sides with other side having a larger apse. A bigger difference, however, is that some religious basilica have transepts. A transept extends a part of the building on the sides to create a cross formation when looking down at the building. This design was popular due to how important the symbol of a cross is to Christians. One of the defining factors for what made a basilica a church was the addition of an alter underneath the apse where the clergy would officiate.

Floor Plan of a basilica with a transept

In obtaining information about these basilicas, it is much easier to generalize about basilicas in ancient Rome compared to the catholic style basilicas. There are some main differences in these ancient basilicas like the fact that the Basilica Maxentius uses vaults while the other basilicas use columns. However, these basilicas had more similarities than differences. They all had a central space with galleries, generally in two stories and had some form of light going through it from the clerestory. They were all made in the same time period of ancient Rome and therefore had the same construction techniques for each building. Religious basilicas, however, cannot be generalized as easy. Their designs can have a great difference between each building. These were made in a much larger time frame (from after the Roman empire to now). Their building materials and techniques can be varied from time period to time period. There decorations can be as varied as well.

Ancient Roman Basilicas

We get a lot of information for these ancient roman basilicas from Vitruvius due to the fact that most of these basilicas are gone and there are very little remains besides a few columns here and there. Some researchers talk about how each new discovery of these basilicas lead to more questions since so little information is available. Vitruvius was an ancient Roman author, architect, and engineer who wrote down a lot of information about the architectural design of many buildings in Rome. He stated that basilicas should be adjacent to the forum in the warmest quarters so they could still be in use in the coldest of days. Vitruvius said that these basilicas would be no longer than three but longer than two times the width of the building (unless some difficulties in the site required the use of other proportions). The side aisles should be one-third the width of the central nave. These basilicas used columns to carry all of the weight of the upper stories and the clerestory. The upper columns would be smaller than the lower columns. With all of the weight transferred to the columns there was no weight transferred to the walls allowing for some basilicas to have no walls. Like a lot of the decorations of these basilicas, they imported marble from places far away to decorate these buildings. The walls (if it had any) were decorated with friezes showing the history of the roman republic. If you were to stand in the middle of the nave you would see the light coming down from the clerestory with only decorated columns on each side of the basilica hiding the friezes on the walls. The foundation and the building materials would be made of concrete with the roof made of wood.

Basilica Aemelia
A good example of these kinds of basilicas was the Basilica Aemelia. This basilica is the only one that has survived from the Roman Republic era and therefore gives us the most information about these ancient roman basilicas. It had two sets of aisles on each side of the basilica with four sets of colonnades. The inner columns had a width of .85 meters with the outside columns having a width of .55 meters. You would be able to go on top of the second floor outside and have a great view of the Roman Forum. The length of the building was estimated to be around 90 meters while the width was estimated at 30 meters. It had two upper stories with the top story having the clerestory. Besides the second set of colonnades to the northern side of the building that were cipolino marble, the columns were made of africano marble. The columns had white marble bases with Corinthian capitals. The pavement of the building was made of various colored marble. 21.2 meters of the estimated 184 meters of hypothetical friezes still exist today. Outside of the building there was a covered area created by barrel vaults where there would be shops because it would face the Roman Forum. This basilica had three entrances. Although this basilica is not the grandest it is a great example of the type of basilicas made in that time.

3D Model of the Basilica Aemilia
3D Model of the Basilica Aemilia

Basilica Maxentius
A major exception to ancient roman basilicas is the Basilica Maxentius or Basilica Constantine. This is the last ancient roman basilica made (Imperial Roman era) and much of its remains still exist today. One of the major differences between this basilica and the others is that it this one used vaults instead of columns to hold up the building. While other basilicas of the time used wooden beams to hold up the roof, this basilica used a combination of barrel and groin vaults. Due to the use of these vaults and the ingenuity of ancient roman architects and engineers some of the vaults still exist today. The basilica is divided into three parts due to three different vaults in each room. The three components of the aisles were separated from each other with each part having a barrel vault. The support of the barrel vaults had an inner barrel vault so the aisle could be connected. The central nave, however, was completely open with the top of it help up by three groin vaults. The weight of the groin vaults was transferred Corinthian style columns. The groin vaults were higher than the barrel vaults so there could be openings in the walls between them that would create a clerestory. The nave measures at 80 meters in length and 25 meters in width. Each of the aisle parts is 23 meters by 17 meters. The roofof the groin vaults reached 35 meters with each of the Corinthian columns being 14.5 meters in height.

Floor Plan of the Basilica Maxentius
Floor Plan of the Basilica Maxentius

Christian Basilicas
After Constantine legalized Christianity in Rome many basilicas were built as churches. These basilicas can be seen just like the older basilicas, a building for public business. The only difference was that the building had religious overtones instead of a purely political or economic one. To understand these building one needs to understand the uses and needs of the people using them. These buildings were mainly used for mass where many people would congregate. While they varied in size and the number of aisles they had (some churches would not have any aisles at all) they were still large buildings that could hold hundreds to thousands of people. An alter was placed underneath the apse for use of certain religious ceremonies by the clergy. Usually the area underneath the apse was elevated so the congregation would have a better view of the ceremony. This area near the apse where all of the clergy and official ceremonies was being performed was called the sanctuary. It served as the focal point of the building where the congregation would concentrate on. They also added atriums in the front of these buildings as well. They would be placed near the entrance of these buildings. They would be designed with the building as an open court where many people could congregate and interact with each other. While columns could still be used for these basilicas (especially the earlier ones) there were many basilicas that used vaulted ceilings. Some of the most famous basilicas in Rome today use a vaulted ceiling using barrel or groin vaults. One of the best examples is St. Peters Basilica that uses vaults to make the area inside the church enormous.

Another component in designing the churches was showing its religious importance as well as its function. Columns can still be used for decoration where they would be highly decorated with marble from around the world. The same was true with the capitols on the columns. The inside of these buildings walls were highly decorated. They put many paintings and murals of religious people and scenes inside these basilicas. These paintings and murals have been seen as some of the most famous artwork in history. As there are many saints in the Catholic Church they would honor them by putting their tombs inside these basilicas making them a monument. Many of these monuments would be placed on the side of the churches next to one of the aisles. Another important addition was a transept that was added to these buildings. People do not necessarily know where the design of the transept started but when they realized the resemblance of these buildings to the cross it was used nonstop. The transept was used to help distinguish the difference between the regular part of the church where the people would congregate for mass and the sanctuary. The area on the sides of these transepts could be used for monuments or merely for decoration.

The capitol of a column from the Basilica of San Clemente

Old St. Peters Basilica
One great example of a traditional basilica style church was old St. Peters Basilica. It was built by the order of the Roman Emperor Constantine and became his greatest building that he built. Construction started in around 330 AD and finished in around 360 AD. The church amazingly lasted twelve centuries and became a major place of pilgrimage due to its longevity and importance. It is claimed that the basilica was built on top of grave of St. Peter who is seen as the first pope of the Catholic Church. It had a central nave that was larger and taller than the side aisles. It had two sets of aisles with a total of four colonnades in all. It had a length of around 110 meters while the height of the basilica in the central nave was around 30 meters. It contained a small transept very close to the sanctuary where they put the relics of St. Peter and his grave On the other side they put a baptistery where they performed religious rituals. While there were barrel vaults used on the side colonnades using columns it was not a vaulted building. The roof was held up using columns and the roof was flat and made of wood. It also contained a large atrium that was in front of the entrance of thebuilding away from the sanctuary. Over the years this church was made gathered a lot of artwork, statues, monuments and graves of famous saints and popes who died through out the years. It became an extremely important and historic building through out the years. As it got older and run down it was replaced by the new St. Peters Basilica.

Floor plan of old St. Peters Basilica

Cross Section of old St. Peters Basilica

New St. Peters Basilica

New St. Peters Basilica gives us an interesting case study in what makes a building a basilica in the architectural sense. It was built on top of old St. Peters Basilica. It started construction in 1506 and was finished in 1626. It was a gigantic construction project with the length of the building being 220 meters. In some sense it can be seen as a basilica using barrel vaults. It contains a central nave that is higher than the side aisles. It uses piers to hold up the roof using barrel a series of barrel vaults on the side and one long barrel vault for the nave. It even has windows on top of the nave making a clerestory. However it is hard to call it a basilica when it contains such a large dome. There are other churches that have domes that are still basilicas in the architectural sense. The difference is the size of St. Peters dome. The height of the dome is measured at an astounding 138 meters. This dome can be seen all around Rome and is a defining feature of the church. It is better to describe the building as a centrally planned church with a basilica feature instead of the other way around. The churches first design was of a centrally planned church. Donato Bramante was a famous architect who designed the first plan of St. Peters Basilica. In its floor plan it was designed as a gigantic doom with smaller dooms built on its diagonal axes. It was not until later designs where the basilica components of the church were added. It was the great Micheangelo who combined these components into the church we see today. On one point of view it can be seen as a basilica where the doom acts as a transept for the building. When seen from the top it can be observed that it does have similarities to the shape of a cross due to the design of the dome. On the other point of view it is seen as a centrally planned church with some basilica additions added on to one side.

St. Peters Dome

Basilicas have a long history in the architectural world of Rome. They have played a huge part for the public from ancient times to now. Its design has affected millions of people over the centuries. It has helped define what is a public building and helped define the building structure use for the Catholic Church. This ancient building shows how powerful and important architecture is today.

“Basilicas of the Forum Romanum: Administrative and Public Meeting Places.” Ancient History Encyclopedia. Ancient History Encyclopedia, 18 Jan. 2012. Web. Sept. 2013.

“CONSTANTINIAN ARCHITECTURE: OLD SAINT PETER’S.” WorldPress. WorldPress, 23 July 2012. Web. Sept. 2013.

“Digital Roman Forum: Basilica Aemilia – Introduction.” Digital Roman Forum: Basilica Aemilia – Introduction. UCLA, 2005. Web. Sept. 2013.

Krautheimer, Richard. “The Constantinian Basilica.” Dumbarton Oaks Papers. Vol. 21. N.p.: n.p., 1967. 115-40. Print.

Perkins, Ward. Papers of the British School at Rome. Vol. 22. N.p.: British School at Rome, n.d. Web. Sept. 2013. <>.

“Roman Basilicas.” Crystalinks. Crystalinks, n.d. Web. Sept. 2013.

Follow us

Don't be shy, get in touch. We love meeting interesting people and making new friends.