This layered maze made up of some 2,400 kilometers of tunnels is the result of limestone mining during the construction of Odesa. The labyrinth has served as a hiding place first for smugglers, then for revolutionaries and, during World War II, for Ukrainian partisans. The Museum of Partisan Glory (commonly called the Catacomb Museum) in Nerubayskoye, just north of Odesa, offers guided tours covering the unusual history of the catacombs. These tours cover only a fragment of the underground network, though the Fagot Travel Agency (Rishelievska 4) runs more-detailed excursions which must be booked a day in advance. For safety reasons, the catacombs can be visited only with guides.