The same water that fills a luxury resort’s pools feeds these free hot springs in the rainforest.

In Costa Rica's cloud forest, the roots of a woody ficus create a botanical bridge.

A tunnel that brings more than a century of history to life from the deepest parts of the Niagara Gorge.

The watery entrance for condemned prisoners heading to the Tower of London is still visible along the Thames.

Six ravens are kept captive (but well-fed) at the Tower of London to prevent the fall of the Crown.

Scattered throughout London are ancient remnants of the city's former bounding wall.

After nearly 60 years, there's still a bear at Paddington Station looking for help.

Kings Cross Station pays tribute to its role in Britain's best-selling book series.

Washington's iconic carousel has a nice piece of Civil Rights history.

Those with a sharp eye can find the hidden image of a German Shepherd on the memorial's Mural Wall.

Housing the National Women's Party since 1929, this historic house is now a monument to the fight for gender equality.

A three-story tower of books about Abraham Lincoln is one of the more unusual monuments to the president.

A monument in Washington D.C. marks the spot from which all other roads were supposed to stem.

There's a 12-foot-tall replica of the Washington Monument hidden under a manhole nearby.

The United States Capitol's former columns still stand.

The site of the climactic scene from the classic horror film is now a historic landmark.

A crumbling Beaux Arts monument to the Bay Area's age of rail.

Beneath the southern end of the Golden Gate Bridge is the “Gibraltar of the West Coast,” a fort built to protect the San Francisco Bay from naval attack.

San Francisco's urban bison herd has persisted in the face of extinction, development, and disease.

In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.

A huge musical instrument played by the ocean.

The world's only teal arches exist in a city that cares more about its aesthetic than an Instagram influencer.

The highest point in Arizona is an oddly snow-topped peak within the otherwise arid state.

The eroded core of an ancient volcano is now accessible by a short hike.