Under the ancient city of Osimo lies a dense network of tunnels, passages, and underground environments dug at various levels. They are connected vertically to each other by wells or chimneys. The labyrinth of caves connects to a few notable palaces such as Palazzo Campana, Palazzo Riccioni, Palazzo Simonetti, and Palazzo Gallo. The 88 caves and a dozen narrow underground tunnels were most likely used as escape passages, food storage facilities, or for the passage of water. The mystery surrounding the origins of these caves is probably due to their secrecy.
There are various symbols throughout the network, from the religious bas-reliefs kept inside the Cantinone Caves, to symbols associated with the Templars from 1167 to 1317. There are also associations to the Knights of Malta. Other reliefs contain esoteric symbolism that refers to legendary places such as Atlantis and the Temple of Solomon.
Among the numerous caves, the galleries under Palazzo Campana contain two that are filled with bas-reliefs containing allegories.