The Roman Empire has had long-lasting impacts on the world around us. From modern European cultures, laws, and languages to the very buildings we all live in and use today. One of their greatest achievements was the refinement of the architectural element called the Capella or Dome.
It was, in its time, a profound leap in our understanding of engineering. Dome design and technology continued to be developed in the Eastern Roman Empire (Byzantine Empire) long after the fall of Rome.
For the Romans, domes would become common features in bathhouses, villas, palaces and tombs. They would also feature a hole or oculus at the top, but not always.
In some cases, like the dome of the Pantheon in Rome, the Romans would create structures that would be unrivaled for almost two millennia.
The Evolution of the Dome in the Roman Empire
Domes are thought to have first appeared as solid mounds and round huts or tombs in the ancient Middle East and India, not to mention the Mediterranean. But it was the Romans who first introduced large-scale masonry hemispheres within their buildings.
The Romans realized that large spaces might benefit from limiting the number of columns or walls needed to support the space's roof. Building on their knowledge of arches, the dome would become one of the defining features of architecture of the Roman Empire.
Large masonry domes exert massive lateral thrusts around their perimeters. For this reason early monumental buildings with domes needed to have massive supporting walls to deal with the stress.
Roman domes tended to be partially or completely concealed from the outside of the building. But in some circumstances, they were covered with conical or polygonal roofs.
Domes would also become monumental in size during the Roman Imperial period.
It would take the splintering of the Roman Empire and the emergence of the Byzantines to take the technology further. Under their continued work, domes were made more impressive by raising them on piers.
This allowed for domes to be transitioned from being built on cubic bases to being supported by a series of pendentives. Pendentives are inverted triangular masses of masonry, which curved horizontally and vertically, that fill the upper corners of a room.
The challenge of supporting a dome over an enclosed square or polygonal space assumed growing importance to the Roman builders of the late empire.
It remained for Byzantine architects, however, to recognize the possibilities of the pendentive and fully develop it. One of the earliest examples of the use of them is also one of the largest—that of Hagia Sophia (completed AD 537) at Istanbul.
Domes would fall out of fashion with the rise of Gothic architecture but would become popular once again during the Renaissance and Baroque periods.
In the following article, we'll explore some of the most interesting and great Domes of the Roman and Byzantine Empires.
1. The Dome of the Pantheon, Rome
The Pantheon in Rome is the best-preserved building from the Roman Empire. It was rebuilt by Emperor Hadrian in 126 AD after previous incarnations of the building were destroyed by fire.
Its most prominent feature is its impressive dome that has stood the test of time. It is a real testament to the skill and genius of Roman architects and engineers.
The dome is famed for its central oculus (eye) that is 30 feet (9 meters) in diameter and open to the elements. Drains on the floors under it help drain away water on a rainy day.
When the weather is more pleasurable the oculus funnels sunlight into a natural spotlight that tracks the inside of the building.
The rotunda measures 42.3 meters in diameter, which is the same dimensions as its height, making it a perfect hemisphere. It is made of light tufa, scoria and cement.
The internal surface of the dome is molded into a series of coffers that both lighten the dome and provide stiffening ribs for added strength.
It would remain as the world's largest dome for almost 1300 years and still the largest unsupported dome in the world.
2. Rotundas of the Red Basilica, Bergama, Turkey
The "Red Basilica" is a largely ruined temple built by the Romans in the ancient city of Pergamon (now Bergama) in Turkey. It is thought that the temple was erected during the reign of Emperor Hadrian.
It is today, one of the largest Roman structures that still survives from antiquity in this part of the world. The temple was most likely dedicated to the Egyptian gods of Isis and Serapis.
The temple is large in itself but would have been part of a much larger complex. The most striking elements of the building still standing are the two impressive rotundas topped with domes on either side of the main temple.
Each one stands at 18 meters with a diameter of 12 meters. Each one has its own 3.7-meter diameter oculus too.
During the days of the Byzantine Empire, it was converted to a church dedicated to St. John and was later partially destroyed.
3. Temple of Mercury, Bacoli, Italy
In the ancient ruins of the old Roman town of Baiae, now called Bacoli, in Italy, there is a remarkably well-preserved dome in the so-called Temple of Mercury.
The town is situated on the northwest shore of the Bay of Naples. It used to be a very popular resort for centuries during the times of the Roman Empire.
Baiae, in fact, is thought to have rivaled Pompeii and Herculaneum for its luxury and attraction of the super-rich.
The town's "Temple of Mercury" has an enormous 21.5-meter dome that is still in pretty good condition.
Despite being called a temple it was actually a swimming pool to a much larger bath building. Like other domes of the Roman Empire, it came complete with an Oculus at the top.
4. Stabian Baths Frigidarium, Pompeii
The baths take its name from the fact that it lies at the intersection of the Via Stabiana and Via dell-Abbondanza of the ill-fated city of Pompeii.
The Stabian Baths is the oldest bath house in the city and have four distinct building phases. The eldest of which is likely the 4th Century BC.
They were built at the time of Pompeii's subjugation to Rome. Under Roman control, they were heavily extended and lavishly decorated.
Most of its existing form is thought to date to the 1st Century BC. One of the baths' most impressive surviving features is its impressive dome atop the frigidarium.
The frigidarium would have been richly decorated in its day with garden scenes. The dome would have been painted blue to represent the sky.
5. Nero’s Domus Aurea dome and Oculus
The Domus Aurea, or Golden House, was an enormous landscaped palace commissioned by Emperor Nero after the great fire of 64 AD. This fire destroyed large parts of the ancient city as well as many villas on Palatine Hill.
The new Domus Aurea complex would cover parts of the slopes of the Palatine, Esquiline, Oppian and Caelian hills and had a manmade lake in the marshy valley.
The "Golden House" was intended as a place of entertainment with over 300 rooms and no sleeping areas. No kitchens or toilets have ever been discovered at the site.
Most impressive of all is the presence of the still intact dome of the Domus Aurea. Two dining areas flank a large octagonal court topped with a dome and giant oculus.
It was constructed using a very early form of Roman concrete.
After Nero's death, the complex was stripped of its marble and other valuables within ten years. It was seen as an eyesore in its day and an embarrassment to Nero's successors.
The entire site was soon buried and built over. The Flavian Amphitheatre (The Colosseum) is built on the site of the old lake.
6. Tempio della Tosse, Tivoli
Tempio della Tosse or, "Temple of Cough", is largely intact Roman construction located near the ancient Via Tiburtina in Tivoli.
Very little is known about the building and what function it served. A plaque was discovered that hinted it was built in the first half of the 4th Century. Perhaps on the site of an older 1st Century BC villa.
It was possibly used as a nymphaeum or a temple to Venus, the Sun or a tomb. Whatever the case may be, it was converted into a church dedicated to the Virgin Mary in the 10th Century.
The building is circular in form topped with a dome very similar to that of the Pantheon in Rome. It measures around 12 meters in diameter, is made of concrete and has a large oculus.
Today it is undergoing restoration and is private property.
7. Dome of Hagia Sophia, Constantinople (Istanbul)
Hagia Sophia in Istanbul, Turkey has one of the finest examples of Roman, technically Byzantine, domes in the world. It has been the subject of great interest for historians, architects, engineers and tourists the world over for almost 1500 years.
Originally commissioned by Byzantine Emperor Justinian the 1st, it was built between 532 and 537 AD. Its most notable feature is its splendid main dome which is considered the pinnacle of Byzantine Architecture.
The enormous main dome is carried by four spherical triangular pendentives on the corners of the square base of the main basilica. So large is the dome that its weight has constantly remained a problem throughout the building's life.
The original cupola collapsed in an earthquake in 558 AD. This was later rebuilt and replaced in 563 AD by Isidore the younger.
Isidore decided to reinforce the new dome with a series of ribs and used lighter materials and increased the height slightly. This dome also collapsed during a later earthquake with some sections to the North and South surviving to this day.
8. Santa Costanza, Rome
Santa Costanza is a 4th Century church in Rome. It is located on the Via Nomentana that runs North to East out of the city.
Round in form it has some of the best preserved Roman mosaics and layout in the world. It is thought to have been built by Constantine I as a tomb or mausoleum for his daughter Constantina who died in 354 AD.
Recent excavations seem to indicate that it was actually built later by Emperor Julian. If true, it is likely the intended burial place for his wife Helena who died in 360 AD. Helena was actually also a daughter of Constantine I.
Although the building is very beautiful in its own right, the main feature is its fantastically preserved central dome. There is also a magnificent ambulatory around it.
The dome itself is shallow, one that is raised on a drum above the main structure of the building.
Despite the loss of the colored stone veneers of the walls, some damage to the mosaics and incorrect restoration, the building stands in excellent condition as a prime example of Early Christian art and architecture.
9. Mausoleum of Galla Placidia, Ravenna
The Mausoleum of Galla Placidia is best described by UNESCO as "the earliest and best preserved of all mosaic monuments and at the same time one of the most artistically perfect".
It is located in the backyard of San Vitale in Ravenna and is thought to have been erected in 430 AD. This makes it one of the oldest buildings in Ravenna.
It gets its name from Galla Placidia who was the daughter of Roman Emperor Theodosius I. She would later marry a Visigoth King and the Roman co-Emperor Constantius III and was for a part the most powerful woman in the western world.
She would later die in Rome in 450 AD and is not thought to have been buried there. Modern opinion is that it was actually built as an oratory rather than a mausoleum.
It is largely cruciform with a central dome on pendentives. The interior of the mausoleum is covered with rich Byzantine mosaics, and light enters through alabaster window panels.
10. Basilica of San Vitale, Ravenna
The Basilica of San Vitale is one of the most important examples of early Christian and Byzantine architecture in the world. The church has been given the honorific of "Basilica" as it is of exceptional historic and ecclesial importance.
The ground was broken in 527 AD with its construction completed in 548 AD. At this time Ravenna was actually occupied by the Ostrogoths. Its construction was financed by Julius Argentarius a banker and architect.
The church has an octagonal plan and features many Roman Architectural elements including its dome, doorway forms, and stepped towers. It also combines Byzantine elements from the apse, capitals and early use of flying buttresses.
It is most famed for its exquisite Byzantine mosaics and forms the largest surviving collection outside of Constantinople (Istanbul).
11. Basilica of San Lorenzo Maggiore, Milan
The Basilica of San Lorenzo Maggiore is an early Christian church in Milan, Italy. Its origins can be traced back to late Roman times and it was refurbished and extended several times throughout history.
Historians believe it was built sometime between the fourth and fifth centuries. Recent archaeological investigations seem to indicate its construction between 390 AD and 402 AD.
The original building's function is still something of a mystery. Some believe it was an imperial basilica, others think that it might have been intended as a mausoleum for a prominent Roman dynasty.
What is certain is that at the time of its construction the basilica was the largest, centrally planned building in the West. The dedication of the temple to St. Laurence (San Lorenzo) the martyr has been certified only from 590 AD. At this time Milan was under the control of the Lombards.
One notable portion of the basilica is the Chapel of Saint Aquilino. This is an octagonal chapel adjoined to the southern part of the main church.
It is thought that this was originally built as a Roman mausoleum and has some 4th Century Palaeo-Christian mosaics. It also has a beautiful example of later Roman domes that survives today.
12. Baptistery of Santa Maria Maggiore, Nocera Superiore
The Baptistery of Santa Maria Maggiore is an early Christian baptistry that is thought to have been built in the 6th Century AD. It was later restored and remodeled in 1856 and the Byzantine style dome was restored in 1944 following damage from the eruption of Vesuvius the same year.
The Palaeo-Christian Bapistry is roughly circular in plan and is very much influenced by the Byzantine style of Architecture. The structure houses the second largest baptismal font in Italy.
It also has a double row of 15 columns, having capitals from other buildings, and supporting a Byzantine-style dome.
The town in which it situated also had a colorful history.
Nocera Superiore is a small town in the province of Salerno in the Campania region of SW Italy. It used to be an Etruscan city that was founded in the 7th Century BC.
The Etruscans would later abandon the area and the Samnites would later recolonize it. It would ultimately be conquered by the Romans in 308 BC.
With the fall of the Eastern Roman Empire, it was besieged and captured by the Lombards in 601 AD.
13. The "Temple of Romulus", Roman Forum, Rome
And last but by no means least on our list of domes of the Roman Empire is one few know exists. Tucked away in the old Roman Forum in Rome is the "Temple of Romulus".
The Roman temple now forms part of the Santi Cosma e Damiano. This is a very early church and a minor basilica that is located on the eastern side of the Roman Forum.
It is dedicated to two Greek brothers, Cosmas and Damian, who were both doctors, martyrs, and saints. The entire building incorporates many Roman Empire era buildings.
The much earlier "Temple of Romulus" is a cylindrical brick building that has a shallow octagonal dome on top. It serves as the entrance to the old Forum from the main church and is rarely if ever, used today.
It is thought that this temple was raised in the early 4th Century. It is possible that the original temple was dedicated to Valerius Romulus who was the deified son of Emperor Maxentius.
It would later become a church in 527 AD and contains important but heavily restored Palaeo-Christian art.