The Panathenaic Stadium was originally constructed around 330 BC to host track events and athletics championships for gymnikoi agones (nude male athletes). Although not much nude racing goes on at the track today, it was also used as the track venue for the first modern olympics in 1896.
The stadium is named after the length of the track, one stade, a measure of length in Antiquity, equivalent to approximately 185 meters. The seating area can accommodate over 68,000 spectators and the rows are all made out of marble. It's an amazing sight to see!