150 years ago, during the reign of Catherine II, Russia began to develop the glass industry. Since 1860, the place called Sablino used to be the center of mining the silica sand. It was hard work. The sand was carried in baskets by hands and sent to the local glass factories. Later came the trains and sand was sent to the nearest railway station. During the World War I and the revolution, the glass industry went into decline, but mining continued sporadically until the World War II.
There are 14 caves in Sablino. Narrow underground passages with the length of 10-15 meters are called Fox holes by locals. The most interesting and longest labyrinths of 5.5 and 3.5 km are located on the both banks of Tosno river.
There are three underground lakes in the caves, the depth of which reaches three meters. The walls of the passages consist of white and red sandstone, and the vaults of glauconitic limestone in some halls are green. Some people believe that the cave air is beneficial to health and prevents many diseases.
Though, the place are located just 40 km from Saint Petersburg, it is not recommended for claustrophobic people to visit. The caves get really tight sometimes.