Odessa Catacombs

The Odessa Catacombs are a labyrinth-like network of tunnels located under the city of Odessa and its outskirts in Ukraine, that are mostly the result of stone mining, particularly coquina. The system of Odessa Catacombs consists of a network of basements, bunkers, drainage tunnels, storm drains as well as natural caves. The Catacombs are on three levels and reach a depth of 60 metres below sea level. It is one of the world's largest urban labyrinths, running up to 2,500 kilometers.
In the 19th-century, most houses in Odessa were built of limestone that was mined nearby. These mines were abandoned and later used, and widened, by local smugglers, creating a labyrinth of underground tunnels beneath Odessa.

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