The 40,000-seater Anfiteatro Flavio was the ancient world's third largest, after the Colosseum in Rome and Capua's amphitheatre. Rising above the congested roads, railways and ugly modern apartment blocks literally and figuratively, it was built mostly during Vespasian's rule (AD 70-79), though work may have started under Nero. The impressive carceres (cells) in the underground area below the arena indicate that the amphitheatre was used for venationes - contests involving exotic animals, shipped in through Puteoli's port from one of the Empire's distant provinces.
The large fossa (ditch) cutting across the arena may have contained the stage scenery, which was raised or lowered depending on the backdrop required. The underground cells are open to visitors, and the cavea (stalls) and the arena are back in use for rather more sedate musical entertainment from June to September; information is available from the site ticket office or the Ufficio Informazioni dell'Azienda Cura Soggiorno Turismo (081 526 1481, www.infocampiflegrei.it). The area around the amphitheatre is scattered with beautifully carved marble fragments found in the Campi Flegrei, a wonderful open-air museum of sorts.