Odessa is located on land that millions of years ago was covered by the Black Sea. Shells of mollusks combined and formed light yellow shell rock. Examining any of this rock, a person can see that it is composed of millions of shells.
Sandstone was both the foundation for the city and a primary building material. Easy to dig through, the sandstone allowed for the construction an estimated 2,000 kilometers of labyrinths stretching out under the city. Nearly the entire older section of Odessa is built with this stone.

The museum guides tell stories of how the catacombs were used as a refuge for slave traders, who smuggled stolen women out of the port of Odessa to the slave markets of Constantinople.

There are no forests or hills around Odessa, during World War II the only place were the Ukrainian partisans could hide were in the catacombs. The partisans used the tunnels as a base from which to attack the occupying Nazi troops. There were five partisan groups and 45 other groups, for a total of 6,000 people, that operated in these tunnels. The partisans killed more than 3,000 Nazis, derailed over 30 trains carrying soldiers and military equipment, and they saved thousands of people from becoming slave laborers.