The Colosseum was begun by Vespasian, introduced to the public by Titus and completed by Domitian. Though the structure stands in ruins today, it has definitely stood the test of time to be an iconic structure that architecture enthusiasts across the globe have bowed down to for centuries.
Gist to the architecture:
The amphitheater is a vast ellipse with tiers of seating for 50,000 spectators around a central elliptical arena. Later in the medieval period, the Colosseum was only used for religious purpose. After the destruction, the Colosseum is now 189 meters in length and width is 156 meters. The overall area is around 6 acres. The perimeter originally measured 545 meters. The exterior height is 48 meters and divided into three floors with 80 arches each, respectively from Doric, Ionic, and Corinthian architectural orders. It had two entrances one in the northeast region named as the porta triumphalis and another one in the south-east region the porta libitinensis. Many large segments had collapsed following earthquakes. The 32 entrances on the north side perimeter wall are still standing. The remainder of the present-day exterior of the Colosseum is, in fact, the original interior wall.
The Colosseum was constructed in an oval shape to allow everyone a good view of the events. The architects came up with an idea of bringing arches and staircases within the building so it wouldn’t be difficult to fill and empty the stadium quickly. With over 80 ways arched, with multiple sets of stairs leading straight to the respective seats so that it would easily be filled and emptied in lesser time. Beneath the seats, there was a tangle of corridors and stairs. The stairways from the first level rose to the second and third levels. Ordinary citizens would enter the building through one of seventy-six arches. The other four were reserved for the emperor and his family to use. This caused the Colosseum to have a very unique design.
With the first design of the Colosseum, there was no actual floor and the events would happen on the ground itself. So then the architectures and the people decide to floor it with some basic underground requirements and that floor was made of stone poles and a wooden floor which has ruined away later. When this floor was installed in the Colosseum it was covered with sand to give the effect of the original floor. The new architecture floor there was a complexity of rooms and passageways where performers would get ready, and slaves would raise and lower animals and people up elevators. Eighty walls radiate from the arena and support vaults for passageways, stairways and the tiers of seats.
At the outer edge surrounding the arcades link each level and the stairways between levels. The construction utilized a careful combination of types: concrete for the foundations, tufa infill between piers for the walls of the lower two levels, and brick-faced concrete used for the upper levels and for most of the vaults.