The arrangement of the area took place in the age of Augustus with the completion of the theatre. The building was began by Caesar and completed between the 13 and 11 BC by Augustus who dedicated to Marcellus, his sister Octavia’s son. In the middle ages it was transformed into a fortress and in the 16C the noble family of Savelli turned it into a palace. It is the remains of this house, which was built by Baldassarre Peruzzi, which are visible today above the old arches. The ancient theatre was cleared of its accretions and excavated from 1926 to 1929. The building was quite large. The two tiers of arches which remain were probably topped by a third row of Corinthian pilasters. They formed the semi-circular part of the building which contained the tiers of seats. The stage, of which nothing is left, backed on to the riverbank. 

The Temple of Bellona, built in 296 BC was a parallelepiped with six columns along the shortest side and eleven along the longest sides and had a frontal staircase up onto the podium. What remains of the temple is the podium dating back to the Augustan age. 

The Temple of Apollo, erected in 431 BC, was restored and rebuilt many times, finally during the age of Augustus by C. Sosio with a structure similar to that of Bellona with two lateral staircases. Its remains are three Corinthian columns of white marble rebuilt in 1940.