The Odessa Catacombs are an estimated 2,500 kilometres of labyrinths stretching out under the city and surrounding region of Odessa, Ukraine. The majority of the catacombs are the result of stone mining.
Most of the city's 19th century houses were built of limestone mined nearby. Abandoned mines were later used and widened by local smugglers. This created a gigantic labyrinth of underground tunnels beneath Odessa, known as the «catacombs».
Today they are a great attraction for extreme tourists, who explore the tunnels despite the dangers involved. Such tours are not officially sanctioned because the catacombs have not been fully mapped and the tunnels themselves are unsafe. There have been incidents of people becoming lost in the tunnel network, and dying of dehydration or rockfalls.
Only one small portion of the catacombs is open to the public, within the «Museum of Partisan Glory» in Nerubayskoye, north of Odessa.
The tunnels are often cited as the reason why a subway system has never been built in Odessa.