Wide view of the interior of the Colosseum. The Colosseum was completed around 80 AD.
A view of the Arch of Constantine (c. 315 AD), with the lines to enter the Colosseum in the foreground - thankfully, we arrived early enough to skip the lines.
The subfloor of the Colosseum where props, animals, gladiators, and others would enter the arena via elevators. This area would have been covered by wooden planks covered in sand to make up the floor.