The Underground Paleontological Reserve of the Odesa National University  n.a. I.I. Mechnikov  was founded in 1968 based on geological natural monument of national significance “Odesa catacombs” established in 1963 (Fig. 1).

Fig. 1. Entrance to the underground nature reserve with a memorial plaque on the wall

The reserved object itself is karst caves filled with red brown clay that contains numerous bones of fossil animals. They were discovered in 1929 during catacomb exploration by the legendary expedition of T.G. Gritsay. Since the first paleontological excavations here in 1932 more than 50 000 bones of ancient animals have been found. These animals lived in this area more than 3,7 million years ago. The bones represent 46 species of animals, among which there are some exotic ones: mastodon, Etruscan rhinoceros, two species of  saber-tooth tigers, hyena bear, dromedary (one-humped camel), giant ostriches, etc.

The materials discovered during the excavations are kept in the Odesa Paleontological Museum and besides, in museums in Kyiv, Baku, Moscow, Saint Petersburg.

Geological monument, underground reserve “Odesa catacombs”, is located in the ancient karst caves and underground quarries, so called “catacombs”, which revealed the caves (Fig. 2, 3).

Fig. 2 Plan of the caves of the underground reserve Fig. 3 Tools for the robot in the underground reserve

Generally the cave that obtained its own name, “Reserve” cave, in 1980 is a labyrinth-like karst cavity (Fig. 4).

Fig. 4. Cave "Zapovednaya": on the left - a general view, on the right - camel bones

Its passages are triangular in section with height of 4-2 m, width along the bottom – up to 2,5 m. The passages are almost completely filled with dense layered red brown clay that contains the bones of the fossil animals. Two ancient entrances into the cave are known today. They are collapse sink holes. One of them is larger, up to 20 m in diameter. The sink holes are densely filled with the clay and limestone blocks. Absolute age of the bones was managed to be established in 2001. It turned out to be 3,7 million years.

The “catacombs” themselves as well as the karst caves surrounding them are of great interest in Odesa. This huge geological outcrop, one of the most exciting monuments of mining and history from early XIX century till the present day, includes unique periods like Civil War of 1917-1921 and Patriotic War of 1941-1945. Living camps of partisans of these periods were preserved underground.

The only preserved mine shaft – authentic entrance to the quarries of the middle of XIX century – and the only authentic underground partisans’ camp are located in the territory of the Reserve.

The only preserved mine shaft – authentic entrance to the quarries of the middle of XIX century – and the only authentic underground partisans’ camp are located in the territory of the Reserve.

To ensure the preservation of unique paleontological remains, comprehensive research has been launched since 2017 to assess the current geological, hydrogeological and environmental condition of the Geological Monument. For this, two wells (Fig. 5) have been drilled in the catacombs on the site of the museum “Secrets of Underground Odessa” and the Geological Monument of National Importance "Odessa Catacombs", which are equipped with autonomous data loggers. Schlumberger's Mini-Diver programmable sensors allow one to measure and record atmospheric pressure, level, temperature and groundwater conductivity.

Fig. 5. A – an overview scheme; B - scheme of location of sites and their borders: 1-quarry, 2 - underground museum "Secrets of underground Odessa", 3 - Geological monument of national importance "Odessa catacombs"; 4 - hydrogeological observation wells.