Roman Theatre of Cádiz

The Roman Theater of Cadiz was built around 70 BC when Lucius Cornelio Balbo "the Elder" from Cadiz, a personal friend and adviser to Julius Caesar, decided, together with his nephew Balbo "the Minor", to extend the limits of the city of Gades , building the Necropolis. An amphitheater and a theater were built in this new district, the latter located in 1980 under the current district of El Pópulo.

The second largest Roman theater in Spain.

The Roman Theater in Cádiz, was discovered in 1980 after archaeological excavations aimed at locating the Castillo de la Villa revealed it. Until then, only a few of its interior galleries had been identified, with no one knowing which building they belonged to.
The theater was abandoned in the 4th century. The Arabs built a fortress on its ruins until King Alfonso X of Castile took it in the 13th century and built part of the medieval city on the ruins.
Source: Wikipedia