Central America's deepest lake is actually a volcanic caldera, surrounded by three volcanoes.

The glacier tucked within a New Zealand rainforest.

Though considered an eyesore by some, this boxy Brutalist high-rise plays a significant role in Sydney's past.

A mouldering Colombian bull ring stands as a reminder of the country's complicated relationship with a brutal sport.

The prototype for all Nazi concentration camps.

Lucerne's central prison was converted into a tourist hotel with a bare minimum of changes.

This functioning parish church is also the site of many concert performances due to its wonderful acoustics.

Norway's oldest cathedral still in use.

The design of this beautifully crafted building was inspired by Norwegian glaciers.

The world's northernmost aquarium looks like it has fallen over.

One of the most breathtaking railways in Europe also takes one of the steepest climbs, from fjord to mountain plateau.

Monuments don't get much more metal than these three giant viking swords planted in a Nordic hill.

One man's exploration of the human form, including the bizarre and delightful "Man Attacked by Babies."

Cold storage for agricultural biodiversity.

Home to three historic ships from the age of Vikings.

This memorial commemorating fallen Swiss Guards of the French Revolution has been called the saddest stone in the world.

It houses the remains of a 17th-century version of the Titanic.

Stockholm's decidedly unique public transit system has doubled as the world's longest art gallery for decades.

The convergence of two currents makes this a surprisingly pleasant getaway in the Arctic Circle.

This "preacher's pulpit" once used for pagan ritual, is home to a new, and dangerous ritual.

Walk 2,300 feet above the ground on the "Troll's Tongue."

Daily jousts and dancing barrel makers in Munich's mechanical clock.

Twisted girders are all that remain of an Icelandic bridge that was wiped out by a combination of volcanic heat and glacial floods.

The picturesque birthplace of Icelandic democracy is drenched in the blood of its brutal past.