Built from 72-80 AD by the emperors Vespasian and Titus, it became the prototype for the modern sports stadium. Contrary to popular belief, it was not used to feed Christians to the lions. The much larger Circus Maximus was better suited for that. Nevertheless, a cross was placed in the Colosseum to honor those who were martyred (wherever it happened to be).
The original floor was wood and had a elaborate system of trap doors and pulleys. The compartments undernearth are still visible and a wood platform was recently built to show where the floor originally sat.