Until around 30bc, there were no purpose built arenas. Fights took place in market squares or in the forum. A central area was cleared as a fighting space while spectators watched from shops, buildings or from temporary stands.
The First Arena
The first arena built in Rome specifically for gladiator fights was erected in 29bc by the politician Titus Satilius Taurus. Because he wanted to flatter the emperor Augustus, Taurus had the name of Augustus carved over the entrance. It worked, Taurus had a long and distinguished career.
The basic layout of all gladiatorial arenas was the same. In the middle was the sand covered fighting area, which was oval in shape. This was surrounded by a wall about four metres tall so that wild animals could not jump out. Above the wall sat the audience. The editor, the organiser of the games, sat in a special stand on the shady north side of the arena.
from "Action File Gladiators" by Rupert Matthews
Buy your copy HERE