In the Vallebuona area there are the remains of the most important Roman monument in Volterra: the theater. It was built at the end of the 1st century. BC, and was able to accommodate over two thousand spectators, who could attend the performances from the steps that have been partially preserved. Many remains of the front scene have also survived, which it was possible to partially reconstruct; behind it there were support rooms and a large quadrangular portico.
Many parts of the building were originally decorated with colored marble and statues, most of which have been lost.
The building was abandoned starting from the third century. AD and with the remains of it, a spa complex was built in the center of the portico, the lower part of which can still be admired today, with its mosaic floors and marble basins.