The hidden wartime headquarters of Adolf Hitler, buried deep in the Masurian forest. Wilczy Szaniec (the "Wolf's Lair") was a vast complex of massive concrete bunkers, now cracked and moss-covered ruins reclaimed by the woods. It's also the site of the failed July 1944 assassination attempt on Hitler. A sombre, fascinating stop — walk the marked trails among the bunkers to grasp the sheer scale of the place.