Dhaka, Jan. 19 -- Hidden among the dense forests of northeast Poland, the Wolf's Lair once served as Adolf Hitler's heavily guarded military headquarters. From this secluded base, the Nazi leader directed major operations during World War II, including the invasion of the Soviet Union. The site is also remembered for Operation Valkyrie, the failed 1944 assassination attempt that nearly changed the course of history.

Today, the vast concrete remains have been transformed into a museum open to the public. Visitors walk along marked paths between shattered bunkers and underground passages, where the atmosphere remains heavy despite the birdsong and greenery that now surround the ruins.

Elsewhere in Europe, former zones of division and dang...