The world's largest key collection features keys to the White House, Frankenstein's castle, and Hitler's bunker.

The remains of an early 1900s dude ranch that operated until the 1970s.

These decaying bridges 1,000 feet high are a reminder of the skill it took to cross the Colorado Rockies by rail.

Paleoamericans built these ancient walls high in the Colorado Rockies as part of an extensive hunting system.

This recently rediscovered Civil War-era submarine was the first to ever sink an enemy ship.

Kentucky, Tennessee, and Virginia meet at this point in the Cumberland Gap.

A massive bur oak tree believed to be some 500 years old is the centerpiece of this quiet urban greenspace.

This overgrown Illinois water park offers a whole new type of adventure.

People escaping slavery passed through the oldest house in Lombard, Illinois on their northbound journey to freedom.

Since the 1700s, this old barrel has acted as a post box that relies on the kindness of travelers.

Building this tragically pointless stone barrier cost the lives of the prisoners made to build it.

The world's first zoo for microbes collecting the horrible and wonderful things living on and around us.

Mysterious stone tower featured in many alternative histories of the New World.

Over fifty whirling pools left by the glacial age.

Within the Saudi Arabian desert lies a 2,000-year-old ghost town made of stone and mud.

Twice a day, the water of the Petitcodiac River flows upstream in a surfable wave.

From Nunavut to Tierra del Fuego, you won't find any lighthouse higher than this one.

This prison on the Maltese island of Gozo is almost 500 years old, and they have the graffiti to prove it.

The explorer Captain Cook may have named it White Island, but the Maori call it Te Puia o Whakaari – The Dramatic Volcano.

A site of natural wonder and flying coconuts in Samoa.

Only place outside China and India where two overhead DC power lines cross.

The world's largest impact crater is mainly eroded but still remembers the planet's violent history.

The remains of what was the most important religious complex in coastal Peru for over a millennium.

Giant disc-shaped gate took 20 men to close off this city in Madagascar.