Roman Theatre, Cádiz

Built in the 1st century BC by Lucius Cornelius Balbus Minor, this is the second-oldest stone Roman theatre in the Empire after Pompeii. With a cavea diameter exceeding 120 metres, it was the second-largest theatre in Roman Hispania. Abandoned in the 4th century, a 13th-century fortress was built over it by Alfonso X of Castile. Rediscovered in 1980, only partial excavation has occurred. A visitor centre opened in 2015 with viewing windows onto the remains.