The Hundred Chambers (Cento Camerelle) are one of the grandest structures of Villa Adriana, and served as a substructure for the enormous artificial square of Pecile.

The first part, twenty meters high, is under the curved north side of the Poecile, then turns and continues along the west side up to the Vestibule; the height gradually decreases, following the original level of the ground.

The substructures are more than three hundred meters long, and seen from below they show a large number of windows or doors, hence the name Cento Camerelle.
Unfortunately they are not open to visitors, and are partly used as a warehouse for various finds, marbles and capitals.

In the eighteenth century, the brothers Liborio and Giovanni Michilli made successful excavations in their properties «near the Cento Camerelle», finding several statues including a Flora, an Egyptian Antinous, an Harpocrates and a Hermes.

They donated them to Pope Benedict XIV for his new collection in the Capitoline Museums, where they are still found today; the restorations, as was customary at the time, reintegrated all the missing parts.

The gift was generously rewarded: the pope granted the Michilli the contract for the sale of tobacco, lasting nine years, which was worth one hundred thousand scudi.

The Hundred Chambers are similar to the Praetorium Substructures. There is a robust retaining wall towards the embankment, which is double in order to create a cavity to dispose of rainwater and protect the rooms from humidity.

Then there are transverse walls arranged like a comb, creating long rectangular rooms; they were divided into two or more floors by wooden mezzanines resting on travertine corbels, which remained in place and can still be seen today.

The rooms were accessible from the outside via wooden stairs and galleries which have disappeared. The plastered walls, opus spicatum floors and multiple latrines prove that the rooms were intended for slaves.
The Substructures of the Praetorium, in a more central position, were to be reserved for the soldiers.

A paved road passes in front of the Cento Camerelle, brought to light on the occasion of the Jubilee of 2000; it is parallel to the large Paved driveway that reached the Vestibule and was one of the monumental entrances to the Villa.

The paved road for the slaves was an independent route, sunken and shielded by a wall to hide it from view; it reached a gallery on the side of the Vestibule, which gives access to the underground service network that connected the buildings of the Villa to each other.

It is a series of cryptoporticoes and corridors that pass under the Vestibule itself and then split to reach the subterranean furnaces that heated the water for the Small Baths on one side and the Large Baths on the other.