Odessa is unquestionably the city with the largest network of underground tunnels in the world. Odessa's catacombs stretch for more than 2500 kilometers (1550 miles). Spend a half-day exploring this fascinating world in the company of an expert guide. Underground works in the region have been performed since the 1830s, when stone was quarried for the construction of the city. Multi-level labyrinths were created at random and, as a result, this subterranean network is a veritable lost world - only parts of which have yet been explored. An area in the village of Nerubayskoye is in the vicinity of the oldest of Odessa's tunnels. It was here that the Partisan Resistance detachment was stationed during the first months of German occupation of the city during the second World War. Today, a small portion of the tunnels are open to the public as a museum dedicated to the partisan efforts. The passages have been restored from the words of partisans who survived, and include various items and artifacts found within the tunnels. Occasionally unaccompanied visitors have been lost in the tunnels never to be located, making a guided tour of Odessa's catacombs a much safer option than leaving a trail of breadcrumbs.