Under the ground

Many interesting things are hidden underground. In Odessa, Ukraine, the man-made caves are scattered more than 2,500-kilometers long. Those so-called catacombs were home to the 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 in a new XL Report.