The Mind-Blowing Architecture and Engineering of Rome’s Colosseum

The Roman Colosseum is one of the most famous and impressive ancient sites still in existence today. Every year, millions of tourists flock to see it, and it has been dubbed one of the ‘New Seven Wonders of the World’. It remains the largest amphitheater ever built, despite being nearly 2,000 years old. It is, without doubt, an engineering marvel. So how did the Romans build such a monument?

A digital reconstruction of the Roman Colosseum alludes to its grandeur in ancient times (nerthuz / Adobe Stock)

The Construction of the Roman Colosseum

The Roman Colosseum was designed and built under the watchful gaze of Emperor Vespasian (69-79 AD). Planning for the Colosseum began in 70 AD, and construction followed soon after in 72 AD. Sadly there is no record of its chief architect.

Construction was completed in 80 AD under Vespasian’s heir, Titus (79-81 AD). Various modifications were then made to the finished Colosseum during the reign of Domitian (81-96 AD). These three emperors responsible for the Colosseum are called the Flavian Dynasty, which led historians to dub the building the Flavian Amphitheater.

The purpose of the Colosseum was to appease the general populace, who were disgruntled with the imperial institution after the rule of Emperor Nero. Vespasian and his successors desired to show the glory and strength of Rome through a magnificent spectacle. They also hoped that if they kept the general populace entertained with enough bloodshed, their grievances would be forgotten.

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An 1870 photo of visitors to the Roman Colosseum. It’s difficult to imagine central Rome like this now! (Public Domain)

The Materials and Siting of the Roman Colosseum

The primary building material of the Roman Colosseum was an estimated 100,000 cubic meters (3.5 million cubic feet) of travertine stone, a type of limestone from Tibur near modern-day Tivoli. On top of this was a similar amount of Roman concrete, bricks, and tuff (volcanic rock).

The Roman concrete was really what allowed the Colosseum to be built so solidly. Modern engineers believe the main reason that the Colosseum is still standing today is because of its solid concrete foundation. The Colosseum was built on a wetland near the Tiber River. The poor soil condition meant that the builders had to dig deep to ensure that the Colosseum was stable. The Colosseum was badly damaged during earthquakes in 443 AD and 1349 AD. However, if it weren’t for its concrete construction and foundation, it is likely the damage would have been much worse.

In addition to all the concrete, around 300 tons of iron clamps were used to hold the large stone blocks together. During the medieval period, many of these clamps were pried from the walls, and the Colosseum is scarred with pockmarks to this day.

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The outer walls of the Roman Colosseum, pockmarked by vandals who removed iron clamps (vredaktor / Adobe Stock)

The Architecture of the Roman Colosseum

The Colosseum was designed to inspire awe in all those that saw it. At its completion, it was not only one of the most complex structures ever built, but also one of the largest. At a time when most buildings were only one story, the Colosseum soared above all else, with 50-meter-high walls (164 feet) that covered an area of 6 acres. The Colosseum was twice as long and one and a half times as wide as a modern football field. These walls, made from white travertine stone, would have glistened in the sun.

The design of the Colosseum followed the three major architectural orders or styles of classical architecture. These date back to ancient Greece; the three styles were originally Doric, Ionic, and Corinthian. The Romans made their contribution by adding Tuscan style, which was simpler than the Doric design, and Composite style, which was more ornamental compared to Corinthian.

In Greek architecture, the orders were predominantly structural, focused on the use of supporting pillars. Roman architecture, on the other hand, focused much more on the use of arches. The three orders became more decorative than structural in Roman usage, evident in the design of the Roman Colosseum’s exterior.

The columns of the ground floor were done in the simpler Tuscan style, while the second floor was done in the slightly more lavish Ionic style. The third floor was the most ornate, utilizing the intricately decorated Corinthian style.

The classic Greek and Roman architecture styles, all used in the Roman Colosseum (Oleksandr Babich / Adobe Stock)

The design of the Roman Colosseum became more stylistically complicated the higher one went. The perimeter is made up of 80 arches on the first three floors. On the ground floors, these arches were, at their largest, 4.2 meters wide (13.7 feet) and 7.05 meters (23.1 feet) tall. On the second and third floors, the arches were the same width, but only 6.45 meters (21.1 feet) tall.

The fourth floor was stylistically different. Rather than arches and columns, the fourth floor was made up of flat panels. While originally thought to be quite austere, recent cleaning has proven the opposite. It seems these panels were adorned with carvings and insets of azurite and bronze.

The Roman Colosseum has two main entrances, which were used for different purposes. The northwestern entrance was called the Porta Triumphalis. The name indicates its use for triumphal processions, and it was also utilized by gladiators entering the arena.

The southeastern entrance was called the Porta Libitinaria. It was named after the Roman goddess of funerals and burials, Libitina, and used to carry out the bodies of those who died within the Roman Colosseum.

The Roman Colosseum’s Interior

The Roman Colosseum’s exterior is impressive, but what was it like inside the Colosseum during its heyday? The centerpiece was the infamous arena, where gladiators, prisoners, and even wild animals fought to the death.

The arena was 83 meters (270 feet) long and 48 meters (157 feet) wide. The floor was built from wooden panels which were covered with sand that came from Monte Mario Hill. The wooden floor also included a number of trap doors, which were used to introduce and remove pieces of scenery during displays, as well as special effects. The arena was surrounded by a 10-foot wall that ended in the first level of seats.

The Colosseum interior in modernity, with recently reconstructed wooden floor over the hypogeum (Takus / Adobe Stock)

While most of the Roman Colosseum was a dazzling white, the arena was built from red and black stone blocks which contrasted strongly with the rest of the building's design. The seating surrounding the arena was split into three sets of bleachers called cavea. Attendees’ social status determined which cavea they sat in.

The highest status Romans, like senators and high-level officials, sat in the podium, which was situated closest to the action. On the same level at the north and south ends were two special boxes. These boxes were for the emperor at one end and the vestal virgins (special priestesses) at the other.

Emperors and elites had lower seats at the Colosseum, closer to the action. Here, Nero is shown giving a thumbs down – bad news for the unseen gladiator! (Patrick Gray / CC BY 2.0)

Above the senators sat the non-senatorial noble class, and above them were the plebeians (ordinary Roman citizens). The richer citizens were granted lower seating than the poor. This lower section was split into different sectors. For example, there was an area for boys and their tutors, soldiers on leave, foreign dignitaries, etc.

During the reign of Domitian, a final level, the maenianum secundum in legneis, was added to the Roman Colosseum. This was the highest level and was a gallery for the common poor, slaves, and women. This section was likely standing room only. Gravediggers, actors, and retired gladiators were banned from the bleachers altogether and were not allowed inside the Colosseum.

All the seating was made from travertine stone, and each seat was around 40 centimeters (16 inches) wide. Spectators were expected to bring their own cushions, if they could afford them. The seating was accessed by stairs, and the halls leading to the outside were called the vomitoria. Some have assumed the name is related to a use of the space for vomiting; however, this is inaccurate. The name vomitoria comes from the way the passages spewed people and spectators out from the stands.

Contemporary sources like the Codex Calendar of 354 stated that the Roman Colosseum could seat up to 87,000 spectators at a time. This may have been an exaggeration; modern estimates put the number at a smaller, but still impressive, 50,000.

Under the Roman Colosseum: the Hypogeum

While the Roman Colosseum is famous for its arena, the most impressive and important feature lay beneath the arena floor. Below the wooden arena floor was the hypogeum, or underground.

The hypogeum was added to the Colosseum during the reign of Emperor Domitian. It was an elaborate network of tunnels and chambers over two levels that was used to house gladiators and animals before the shows. This was no small undertaking, and it seems that the network was repeatedly restructured and improved upon. There are at least twelve evident phases of construction.

Eighty vertical shafts connected the hypogeum to the arena; these were used to send caged animals and pieces of scenery to the arena. Larger hinged platforms were used to transport bigger animals like elephants to the arena floor.

Centuries ago, this tunnel was used to transport gladiators or animal combatants up to the arena floor via an ancient ‘elevator’ that was located on the floor stones (Dennis Jarvis / CC BY SA 2.0)

There was also a large amount of impressive machinery inside the hypogeum. Elevators and pulleys were used to carry the animals and scenery through the vertical shafts to the arena floor. There were also massive hydraulic mechanisms that could be used to rapidly flood the arena through a connection with a nearby aqueduct! This flooding was used to put on naval battle reenactments within the Roman Colosseum, which surely would have been something to behold. Sadly, the hypogeum came at a cost. The tunnels meant the arena floor could no longer be flooded, putting an end to these impressive naval battles.

The Naumachia or naval battles, conducted in a flooded Colosseum, 1894 painting by Ulpiano Checa (Public Domain)

Finally, the hypogeum acted as a discrete means to connect the Roman Colosseum with the outside world. Animals and performers could be brought from nearby stables, and the Colosseum was connected directly to the gladiator barracks at Ludus Magnus. Finally, the tunnels could also be used by the emperor and his vestal virgins, so that they didn’t have to cut through the throngs of commoners waiting outside.

Who Built the Roman Colosseum and Who Paid for It?

While there are no receipts tallying the cost of the Roman Colosseum, we do have some idea of how Vespasian and his successors paid for it. In 70 AD, the first Roman-Jewish War ended. During this time, the Jerusalem Temple was raided and sacked by Roman soldiers. It is believed that the Colosseum was at least partly financed by this looting. An inscription of the Colosseum itself states, “The Emperor Titus Caesar Vespasian Augustus ordered the new amphitheater to be made from the (proceeds from the sale of the) booty.”

It is also likely that costs were kept down through the use of slave labor. For a long time, it was believed that the Colosseum was built by 100,000 Jewish slaves who had been captured during the siege of Jerusalem. However, there are no contemporary sources to support this claim, so it is unknown for sure who built the Roman Colosseum.

Conclusion

The Roman Colosseum’s legacy is undeniably bloody. Likely built by slaves and paid for with blood money, it was used to host blood sports and executions. However, it was also used to showcase beauty through Sylvae, recreations of natural scenes used to show an urban population what the outside world looked like.

Even today, in its more diminished form, the Colosseum still inspires wonder. At its prime, it must have been absolutely astonishing to the common plebeians who visited it. The Colosseum and its design give us a window into life in the ancient Roman world, a world as full of genius and beauty as violence and bloodshed.

Top Image: The Roman Colosseum’s architecture remains awe-inspiring today, with more still to be learned. Source: daliu / Adobe Stock

By Robbie Mitchell