“Polish Tuscany” hides a dark secret underground: a Nazi city now ruled by bats

Vineyards ripple across the hills of Zielona Góra, a city known as “Polish Tuscany” for its landscapes and annual wine festival. Few visitors realize, though, that just beneath this beautiful setting, a vast military labyrinth stretches for miles.

Inside the hidden Nazi lair

As Pavlo Fedykovych explains for CNN Travel, the Ostwall, a subterranean fortress commissioned by Adolf Hitler in the 1930s, was designed to hold back Poland and the Soviet Union. Engineers envisioned a defensive line nearly 50 miles long, reinforced with more than two million cubic feet of concrete. For a time, uniforms, bunks, and railway stations filled the tunnels, but by 1938, Berlin’s focus had shifted west and construction slowed. When the Red Army stormed the frontier in 1945, the “invincible” stronghold fell in just three days.

What remained was a ghost city under the fields. For decades it slipped in and out of use, briefly a Polish army outpost, later a hangout for underground subcultures who left graffiti and stories of raves in the 1980s. At least five people died in accidents there.

Bats fill Hitler’s fortress

Then came new rulers. Scientists began counting bats in the 1970s and soon realized the scale: tens of thousands migrate here each winter, huddling in the cold, damp shafts. Today some 40,000 individuals from 12 species make the Ostwall one of Europe’s largest hibernation sites.

The complex has since been reinvented as a dark-tourism attraction. Tours range from gentle train rides to all-day “extreme” treks through the tunnels. Above ground, visitors can raise a glass of local Riesling; below ground, they descend into a fortress where history, counterculture, and nature have collided in eerie harmony.

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