On October 17, 1814, a 15-ft. wave of beer ran rampant through the streets of London.

Scotland's oldest purpose-built concert hall houses an incredible collection of ornate, centuries-old keyboards.

Many of Edinburgh's more unsavory characters spent their final days behind this door while awaiting their executions.

This charming old building's loose connection with the Scottish Reformer is what saved it from demolition after it split apart.

The solemn exterior conceals an opulent interior of this 17th century church.

A rooftop restaurant hides in plain sight atop Vienna's Palace of Justice.

Tall columns of volcanic basalt make up this improbable-seeming rock formation.

Every part of this unusual home is built into the sandstone rock.

These 17th-century mummies are no longer naturally preserved, but remain on display today.

This unusually shaped mountaintop tower looks like a UFO floating over the city.

The walls and ceiling of this Polish church are decorated with thousands of skulls, with another 21,000 skeletons just below.

Folklore says this medieval fortress was plopped atop a portal to hell to trap the demons below.

Mummified monks and the accidentally interred, in a 17th-century crypt.

The world's greatest slide descends 18 stories from this looping mountaintop viewing platform.

Bohemian paradise covered in majestic forests.

Thirty creepy ghosts now inhabit this decaying 14th-century church.

Europe's largest natural bridge has a 19th century royal chateau built into its side.

Europe's second largest ossuary wasn't discovered until 2001.

Underneath this small church are 15,000 bones, arranged by an obsessive academic.

A church of bones, decorated with 40,000 human skeletons.

A museum of alchemy and a basement laboratory all housed in an ancient building in a Gothic tower.

This Czech church doubles as something of a permanent fashion exhibition for a statue of the Infant Jesus.

A crucified and bearded female saint.

Looming communist pillar with a Czech twist.