The old Niles Canyon Aqueduct in the San Francisco Bay Area is a bemusing and secret trail through nature for wayward travelers.

A giant gun barrel in Barbados that once hoped to shoot outer space with science.

The longest and steepest staircase locks in the United Kingdom.

Small plaque marks the spot, but the true center is located about half a mile away on a private pig farm.

A sense of bewilderment encounters visitors when they happen upon this former railway bridge.

Amid the bustle and noise of the Financial District hides a secluded garden oasis above the city streets.

The world’s oldest surviving single-arch railway bridge.

The remains of Crystal Palace Great Exhibition of 1851.

This fantastical house shaped like a seashell brings aquatic design to architecture.

This museum features the original car used on the Beverly Hillbillies sitcom.

Two gems of Beaux Arts architecture that have been sitting vacant for years.

A floating cat sanctuary on an Amsterdam canal.

This ancient settlement contains some of the largest earthen mounds in North America.

This Iron Age hill fort remained hidden until a series of storms revealed its history.

This unusual subway stop was originally a real estate office.

A modern zoetrope on the New York City subway.

Hidden in plain sight on a pair of Manhattan subway tunnels are a pair of public instruments that sing to each other.

A southern Swedish island is home to the last ERSTA artillery battery, meant to protect the shoreline during the Cold War.

The site of a famous samurai duel.

More gold than anywhere else, ever.

In a 345-million-year-old cave that's 200 feet underground, dinner awaits.

This once-popular otherworldly landscape was formed by one of the largest volcanic eruptions in history.

Double spiral staircases are not unheard of, but they are very rare.

Climb to the top of this spiritual tower, and you'll be rewarded with spectacular views.