Architecture of the Colosseum

The Colosseum is one of the greatest feats of Roman architecture ever built. It is the largest Roman amphitheater in the world and despite suffering multiple fires, earthquakes, and other natural disasters –as well as substantial mistreatment at the hands of men– it is still standing today.

The Colosseum’s wall shot from below, with Corinthian columns standing out prominently
The external wall’s third and fourth levels. Notice the decoration on the top of the columns, do you know what style that is?

Construction of the Colosseum

The Colosseum was built between 70 AD and 80 AD under Emperors Vespasian, Titus, and Domitian, the Flavian Emperors. Hence its original name, the Amphitheatrum Flavium – the Flavian Amphitheater.

The Colosseum can be viewed as a populist undertaking by Vespasian who, at least in part, commissioned it as a means to regain the favor of a citizenry that was restless and unhappy with the imperial institution after Nero’s reign. Planning began in 70 AD and construction in 72, on the site of the artificial lake Nero had constructed as part of the Domus Aurea.

Most of the labor for the construction of the building was provided by Jewish slaves, who had been taken as prisoners following the first Jewish-Roman war.

The building was oval-shaped and set on a north-west to south-east axis, with its main axis measuring 189 meters and its shorter one 156 meters. For reference, that is almost twice as long and 1.5 times as wide as a modern football field.

What was the colosseum made of?

The Colosseum was built from an estimated 100,000 cubic meters of travertine stone, plus a similar measure of Roman cement, bricks, and tuff blocks. Travertine is a class of limestone that draws its name from Tibur (near modern-day Tivoli), where it was mined.

In addition to the different types of stone and cement, an estimated 300 tonnes of iron clamps were used to bind the large blocks together. These clamps were scavenged in later centuries when the Colosseum fell into disrepair, leaving large pockmarks in the building’s walls that are still recognizable today.

Style of the Colosseum

The Colosseum was conceived as a testament to Rome’s might. At the time of its completion, it was the most complex man-made structure in the world and one of the largest.

The travertine stone used as the primary material in its construction was white, and at nearly 50 meters in height (at a time when most buildings were single-story) and with a footprint of 6 acres it would have gleamed in the sun and inspired awe in anyone who laid eyes upon it. Its effect on an ancient Roman viewing it for the first time would have been the same as standing at the foot of the Empire State building today.

All three of the major architectural orders of the time were represented:

  • The ground floor columns were done in the Tuscan style, a Roman variation on the austere Greek Doric style.
  • The second floor featured slightly more elaborate Ionic columns.
  • The third floor employed the more intricate and decorated Corinthian style.

Therefore, from bottom to top, the Colosseum went from lesser to greater stylistic complexity. Each half-column was the centerpiece of an arch, of which there were a total of 80 forming the external perimeter of the building on the first three floors. These were largest on the ground floor, at 4.2 meters wide and 7.05 meters tall. On the two upper floors they were the same width but slightly shorter, 6.45 meter tall.

Unlike the first three, the fourth floor wall was not made of arches and columns, but rather of flat panels, which thanks to recent cleaning efforts we know were decorated with carvings and insets of azurite and bronze.

The Colosseum had two main entrances: the northwestern Porta Triumphalis, which as its name suggests was the gate used for triumphal processions and through which gladiators entered the arena, and the southeastern Porta Libitinaria, named for the Roman goddess of funerals and burial Libitina. This gate was used to removed the bodies of those who perished on the sands.

Illustration of the head part of the three types of columns common in Roman architecture: Doric, Ionic and Corinthian
The three orders of columns in Roman architecture.

Inside the Colosseum

The Colosseum’s most distinctive feature was the arena upon which gladiators, prisoners, convicts, and wild animals fought and died.

  • It measured 83 meters in length by 48 meters width.
  • The arena floor was made of wood panels, covered with a layer of sand which was drawn from the nearby Monte Mario hill.
  • There were many trap doors in its floor, which were used to introduce and remove elements of scenery and for special effects.
  • It was surrounded by a 10 foot wall which led to the first level of seats.

The arena wall was made of red and black stone blocks, marking a strong contrast with the rest of the building which was intensely white, and mirroring what transpired on the arena floor.

Surrounding the arena were the terraces or bleachers, collectively known as the cavea. The cavea was divided into three tiers that reflected the social strata of Roman society.

From bottom to top, the podium, gradatio, and the porticus. The seats closest to the arena, the podium, were reserved for Romans of the highest status, such as senators and high ranking officials. As you climbed higher up the cavea you would encounter people of lower and lower social standing, with the top tier being occupied still be Roman citizens, but those who were poor.

Seating was made from travertine stone, and each seat was approximately 40 centimeters wide. The wealthier attendees would bring cushions with them to place on their seats. It is believed that the Colosseum could sit as many as 80,000 spectators.

The cavea was also divided horizontally by accesses for the public; scalaria, stairs, which led to the stands, and vomitoria, passages leading to the exterior. Contrary to popular belief, the vomitoria were not spaces for vomiting. The name refers to the action of spewing forth people, spectators, from a location — but not the contents of their stomachs.

The Colosseum underground

While the Colosseum’s most distinctive feature was the arena, it’s most important was the hypogeum, its underground area.

  • The hypogeum was a network of tunnels and chambers distributed in two levels where gladiators and animals were kept before appearing in the arena above.
  • It wasn’t part of the original design as conceived by Vespasian and his son Titus. It was added after the building had already been inaugurated in 80 AD on orders of their successor Emperor Domitian.
  • 80 vertical shafts connected the hypogeum to the arena above. Gladiators and animals could access the arena through these shafts.
  • Some of these shafts incorporated a system of large moving platforms, called hegmata. These were used to move large beasts such as elephants up and down.
  • The hypogeum was connected to the outside through a network of underground tunnels, such as to the gladiators’ barracks and to nearby stables where animals were kept.
  • The Colosseum had a private access tunnel for the Emperor, so he could enter and exit the building safely, avoiding the large crowds.
  • With the construction of the hypogeum, it became impossible to flood the arena and therefore to hold naumachia (mock naval battles) in the Colosseum. Two were held before its construction.
The hypogeum’s maze-like passages viewed from the Colosseum’s ground floor level
The hypogeum’s maze of chambers and passages is now uncovered and can be viewed from above ground, and visited on guided tours of the Colosseum.