The limestone mining in Odessa started in the beginning of 19th century. The mining was chaotic and unsystematic. It caused severe problems, since part of the city was built on quarries. Several large systems are outside the city. The Odessa catacombs have been the hiding place for partisans during WWII. In the part below the city, the catacombs intersect bomb shelters, utility tunnels, and hill drains.
The first few shots are from Holodnaya Balka. These first photos are from the contest in 2009.
The hill drains (used for draining groundwater) below the city:
Some bomb shelter
Oh. This has nothing to do with the underground, but H. wanted to see if the police really care. He was freezing when eventually the police arrived and asked him kindly to get out of the fountain not to damage his health.