The French excavations conducted till the early part of this century, 1810-1814, showed the general character of the chambers and passages under the arena. They consist of one central passage which extends under the arena from end to end in the line of the major axis of the ellipse. Parallel to this there are four narrower rectilineal passages on each side connected with each other by archways and surrounding these are three curved passages following the elliptical curves of the sides of the amphitheatre. The material of which these walls were originally built was great blocks of travertine similar to those in the surrounding construction of the amphitheatre, but they have been patched and propped in many places with tufa stones and brick, and now present a strange miscellaneous mass of masonry. These underground passages are similar to those found under the arena at Pozzuoli and Capua. It would seem that they must have been necessary, in addition to the chambers under the staircases of the building, for keeping wild beasts in large numbers, or for marshalling and arranging the long processions which were sometimes exhibited in the arena, or for other unusual exhibitions requiring more room for preparation than could be otherwise afforded. In the amphitheatre at Verona the passages under the arena seem to have served the purpose of drains, as they are much less extensive than those under the Coliseum, and are apparently connected with the channels which conducted the rain-water from the upper part. The same is the case with those at Pola in Istria, but at Pozzuoli and at Capua the hypogæa are of a similar character to those in the Coliseum, and were evidently used in connection with the exhibitions on the arena.