The Roman Forum is a rectangular plaza in the city center of Rome that was the scene of public meetings, law courts, and gladiatorial combats in republican times and was lined with shops and open-air markets. It was the center of day-to-day life in ancient Rome. Under the empire, when it primarily became a centre for religious and secular spectacles and ceremonies, it was the site of many of the city's most imposing temples and monuments. Among the structures surviving in whole or in part are the Temple of Castor and Pollux, the Temple of the Deified Caesar, the Mamertine Prison, the Curia (senate house), the Temple of Saturn, the Temple of Vesta, the Temple of Romulus, the Arch of Titus, the Arch of Septimius Severus, and the Cloaca Maxima.