In the city of Tarragona,the ruins of a massive structure stand by the water's edge. Built in the moment century, this amphitheater once held up to 15000 spectators for various events including brutal gladiator fights.
From a distance this structure looks like a semi-circular Roman theatre, and but the original scheme was a complete oval. It was located external the city,near the forum and the entrance of the town. The reason for its current appearance is that in the sixth century a Visigothic basilica and in the 12th century a Romanesque church were built on the site, destroying about half the terracing. One can see evidence of both the later buildings and where the stonework of some of the terracing has been removed.Despite the changes, and can still see part of the elaborate underground system whereby wild animals or additional combatants could be introduced into the middle of the arena via trapdoors and elevators.
Today,visitors can explore the site and learn about its history. It is used for a number of events, including some spectacular mock gladiator fights.
Source: atlasobscura.com