The Colosseum, Rome, Italy

The Colosseum or Coliseum, also known as the Flavian Amphitheatre  is an elliptical amphitheatre in the centre of the city of Rome, Italy. Built of concrete and stone, it was the largest amphitheatre of the Roman Empire, and is considered one of the greatest works of Roman architecture and engineering. It is the largest amphitheatre in the world. The Colosseum is situated just east of the Roman Forum.  Source