A stone age atrium

If 'MTV Cribs' had traveled back in time 70,000 years, this skylit space is just the kind of Paleolithic pad they'd have toured. Archaeological evidence suggests Devetàshka Cave, in modern-day Bulgaria, housed human denizens from the Middle Stone Age until at least 6,000 BCE. After its rediscovery in the 20th century, Devetàshka was unceremoniously repurposed as a military warehouse, but was soon given back to nature. Now a protected site, this karst cave's days of human habitation are probably over. But it's home to a bustling crowd of another kind: Some 30,000 bats make their home in the cave's depths.