A photo from open sources
It is believed that World War II was a war of motors. However until its beginning, all future participants built along their the borders of the defense line, the so-called fortified areas. Everyone knows the Maginot Line and the Stalin Line. Less well-known Meseritsky fortified area, erected Nazis on the border with Poland. In the documents of the Third Reich, he It was called the Den of the Earthworm. 
Photos from open sources
In 1927, the Germans on the eastern border with Poland began construction of a grand scale system fortifications. The fortified area was supposed to cover Germany from a possible blow of the Polish troops. In 1927, the Polish the army, which had recently stopped the Red Army on the approaches to Warsaw, It was considered one of the strongest in Europe. So what concern the German military about the security of the eastern borders was well founded. To the dense marshy area of Lake Kenszyck several thousand workers arrived. The project involved the creation of military camp and more than 100 firing points with a density of 6.6 points 1 km, a system of drawbridges, dams, water channels, dams and more than a hundred kilometers of underground tunnels. Firepower ur were automatically retractable giant flamethrowers, 149 mm armored howitzers and mortar mortars with electric management. The total length of the line is 80 km. To deliver huge the amount of building material was specially built railroad, which went around settlements. 
Photos from open sources
One after another, anti-tank barriers began to appear, gouges and bunkers, machine-gun points covered by armored caps. By the beginning of 1935, UR included more than 50 reinforced concrete blockhouses connected by a network of underground communications. Under the ground at a depth of 60-70 m. A whole a city with dozens of barracks, kitchens, hospitals, food warehouses, its own power plant and fuel storage. In tunnels 2 narrow gauge railways were laid along which an electric train ran. Metro had 17 stations. Under the ground could hide up to 5,000 human. In 1939, the intensity of construction began to decline. Hitler said: “In the east I do not need fortresses, but tank divisions! “Soon the question was decided by itself. In 1940,” construction Reich “was stopped, the underground fortress was mothballed. After no one remembered the Lair war for a long time, until in 1951 the Soviet command did not decide to place in the remaining military town motorized rifle brigade. At the same time, we decided to examine underground part of Ura. The sapper officers who came down to the ground gasped. Tens of kilometers of underground tunnels, freight elevators, hundreds premises, ventilation system. Part of the tunnels was blown up, part flooded. Since 1992, today the “Lair” – historical and tourist a complex along which a guide leads tourists. However big part of the complex is still closed. Still does not exist reliable scheme of the underground city. Constantly detected earlier unknown premises of unknown purpose. Among the “wild” tourists are often victims. And it’s not about ingenious traps, arranged by the Nazis. Grilles on numerous ventilation hatches and freight elevators have long decayed, metal railings, staples break at the slightest load. And often a walk through the apparent safe corridor ends with a flight to nowhere. Therefore local the authorities are trying to brew, concrete all external entrances to dungeon but diggers come for thrills constantly find unaccounted manholes. As for military value fortified area, then in February 1944 the Red Army took “impregnable” fortress in three days.
War poland
