Nazi Ostwall Fortifications
Around the town of Miedzyrzecz Poland  are the remains of an extensive system of bunkers, tunnels and fortifications . These fortifications were built on Adolf Hitler's orders between 1933 and 1938 and extended and improved in 1944 as an eastern wall protecting Germany from invasion. Hitler himself visited the fortifications in 1935.
The Ostwall fortifications consist of a triple line of fortiications and about 100 fortification units connected by underground tunnels 15 to 40 meter deep. These tunnels are so big that double track railway system was able to operate underground. The defences themselves consisted of reinforced concrete bunkers (panzerwerks), several floors high, topped by armoured domes equiped with cannons and machine guns. The whole system was serviced by electricity, water, sewage system, and ventilation. 

Since Jan-2015