From Austrians to Nazis to Soviets, this historic Budapest fortress has a history as complex as the city itself.

Once the home of a hermetic monk, this cave now houses a small church.

This Hungarian castle was built out of cardboard and wood until it proved so popular that it got upgraded to stone.

One of downtown Berlin's last reminders of its Communist past.

Cold war icon and onetime "hole" in the iron curtain.

Thousands of coffin-like pillars make up this controversial Holocaust memorial.

The largest free-standing aquarium in the world resides in a hotel lobby in Berlin.

The most visited, and possibly most controversial, museum in Germany.

This whimsical statue dumps water on its head to symbolize knowledge flowing into his brain. Or maybe booze.

A giant bug impaled on a 75-foot-tall needle.

A Nesting Doll of Churches.

More sculpture than building, this architecturally significant temple was built on the spot of Saint Peter's crucifixion.