Built at the period of Vespasian, but probably inaugurated under Nerone, the Flavian Amphitheatre of Pozzuoli is a unique documentation of the service systems of this entertaining place thanks to the underground system that has preserved its structure.
The Flavian Amphitheatre at Pozzuoli is the third largest after the Colosseum in Rome and the Santa Maria Capua Vetere in Capua.
The amphitheatre could contain up to 20,000 spectators and they could get into through an elliptical portico based on a stalls made of travertine blocks.
The arena had a complex scenic structure consisting of underground passages, steps, and mechanisms for lifting the boxes full of wild animals along the elliptical passageway where trapdoors communicating with the arena were opened. There was also a mechanism for displaying naval battles in the so-called Cardito pool composed of two tanks. The larger one, with a square floor plan and a vaulted ceiling supported by 30 pillars, was filled with water from the aqueduct while the second cistern consisted of 14 communicating mini-pools.
In the northern sector of the underground area is the chapel dedicated to Saint Gennaro, built in 1689. According to tradition, the martyred saint was exposed in vain to the assault of the wild animals, before being beheaded in the church dedicated to him outside the city walls of Pozzuoli.