Under the ground
Many interesting things are hidden underground. In Odessa,Ukraine, man-made caves are scattered across the region and are two and a half thousand kilometers long. These so-called catacombs were home to partisan bases during World War II. In Vladivostok – the main Russian military naval base in the Far East – engineers built a fortress at the beginning of the 20th century. Also, the largest underground Russian church is hidden in Penza. Find more details on RT.