Odessa catacombs is a huge network of artificial underground tunnels and labyrinths under Odessa and its suburbs, the length of which is now estimated at 2.5-3 thousand. Km (1500 – 1900 miles). One of the largest underground labyrinths in the world. For comparison: the catacombs of Paris reach 500 km (310 miles) Rome – 170 km (105 miles).
Most of the catacombs (95-97%) are former quarries where the building stones were excavated, since the 1830s. In 1860s, an extensive network of abandoned limestone mines appeared under the city. The system of catacombs also includes the caves of natural origin, exploration and construction pits, bunkers, drainage tunnels, storm sewers and other underground cavities.