When it was built in 1929, this historic bridge was the only place to cross the Colorado River for 600 miles.

Five painted skeletons are hiding behind a church in this tiny village in the Italian Alps.

A marble Lucifer hides behind the pulpit of this Gothic cathedral.

One person's lost luggage is another person's treasure.

Built to transport German U-boats through the never-completed Masurian Canal, the locks near this Polish village are now home to a rope course.

This Native American settlement dates back to the Pueblo II period.

A fantastic example of Victorian railway engineering with two unusual decorative features.

A replica of a beloved, delicately-balanced granite boulder.

A hidden slot canyon in the southern Nevada desert makes an unexpected oasis and scenic hike.

European castle ruins in an American state park are actually the product of death and grief.

A series of caves, tunnels, and wells filled with fascinating figures and symbols.

A tunnel with windows, so you don't miss out on the impressive views.

A hulking remnant of Alaska's industrial gold mining boom in the 1920s.

US-50 in Nevada is known as "the Loneliest Road in America," but this earlier iteration of the route is even lonelier.

A paradise hotel turned from opulent to overgrown.

An Aztec temple, the largest man-made pyramid in the world, sits buried in earth with a Spanish church set on top.

This 170-year-old Swiss guesthouse built into the side of a mountain is best accessed by a cable car.

Running since 1864, this clock has yet to be wound, one of the longest-running science experiments known.

This lab's maddening silence is good for business but bad for sanity.

These old stone ruins in the Oregon wilderness were once bathrooms and are steeped in legends of murder.

This sword isn't waiting for a king to pull it out. It was placed there by a saint.

Legend says this sacred tree was a gift from goddess Athena.

The beehive-like buildings of this abandoned resort reside near the border of Mauritania and Senegal.

An engineering error ensured this cavernous 350-foot-long subterranean thoroughfare was never used as intended.