This Croatian fairytale castle is slowly falling apart thanks to years of neglect.

This truly palatial work of Communist-era architecture now sits crumbling on a Croatian beach.

A former top secret military tunnel is now stuffed with snow and open year-round to skiers.

Stockholm's last remaining paternoster elevator.

A tour of underground Berlin takes you through WWII air raid shelters and tunnels used to smuggle people out of East Germany.

Sweden's first nuclear reactor, R1, can be visited 25 meters underground.

Islanders once used this dramatic, otherworldly landscape to hide their cattle from Viking raiders.