 They were used as a source of cheap construction materials.Limestone was cut using saws, and mining became so intensive that by the second half of the 19th century, the extensive network of catacombs created many inconveniences to the city.After the Russian Revolution of 1917, stone mining was banned within the central part of Odessa (inside the Porto-Franko zone, bounded by Old Port Franko and Panteleymonovskaya streets).