The colosseum had what type of floor

The Colosseum was built on flat area on the floor of a low valley between the Caelian, Esquiline and Palatine and Velia Hills. An artificial lake which had been created by the emperor Nero had to be drained and filled. Local water streams were canalised. The lake had been fed by a water source from the foundation of the Temple of the Divine Claudius on the Caelian. Thus, the local streams had to be canalised. Concrete was used to provide a solid foundation for the seating (which had a concrete shell).

Underneath the partly brick and partly wooden floor of the arena (which wa86 ? 54 m., 272×157 ft.) where the gladiatorial fights and the animal hunts were performed there was a hypogeum (which means underground). This was a complex underground structure with 12 curved tunnels on the sides of a central passageway. The gladiators and caged animals were housed there prior to the show. It also stored machinery and props for sceneries. On four of the tunnels there were 80 shafts with hoists to lift machinery and the animals up to the arena.

The hypogeum had separate entrances:

·Tunnels underneath the central axis of the Colosseum gave access to both ends of the central passageway of the hypogeum. They were used to bring in machinery and the animals.
· Two monumental entrances gave direct access to the arena for the entry in great pomp for the gladiators. They were also used for animals which were too heavy to be hoisted from the understructure.
·The attendants to the game gained access to the arena though open entrances on a tunnel which run underneath the bottom ring of the seating. This tunnel was also used by the senators to reach a platform reserved for them without having to mix with the crowd.