Located in the valley between Aventino and Colle Palatino, this ancient Roman chariot racing stadium was not only the first of its kind but also the largest. At its peak, the Circo could hold 250,000 people, which was roughly one quarter of the city's population. In 140 C.E. one of the upper tiers of the circus collapsed and killed 1,112 spectators. This tragedy has stood the test of time and remains the wrost sports-related disaster in history, not England vs. Hungary in 1953, as some people would like to believe. I'm looking at you, Dad.