This tiny island featuring 9th-century Viking ruins is only accessible at low tide.

An otherworldly, fossil-rich cobble beach holds Viking graves, cairns, and other remains.

A total of 999 stairs lead visitors through a massive hole in a mountain known as the Gateway to Heaven.

This clifftop arch is a natural stunner.

The "Black Arch" guards the entrance to the picturesque Glens of Antrim.

Unlike most arches, this geological oddity formed in a volcanic dike.

The largest lake in the Faroe Islands seems to be held hundreds of feet above sea level thanks to an optical illusion.

A roadside attraction filled with an astounding array of gloriously wacky vehicles.

The remains of a grand castle that may have inspired Bram Stoker's Dracula.

These otherworldly caverns form Earth's oldest known cave system.

Meant for a railway that was never built because of the Great Chicago Fire, these piers still stand nearly 150 years after they were installed.

These structures were inspired by both Native American shelters as well as, strangely, an ice cream shop.

Most-visited and most-photographed slot canyon in the American Southwest.

This 1,300 year old monastery built atop a single rock was once only accessible depending on the whims of the tide.

A small house sits between two huge rocks, with its back to the sea.

This local celebrity earned his fame by doing a job no one else dared.

This edgy museum will whet your appetite for the industrial history of Western New York.

See the rare bloom of the "Queen of the Night" cactus at one of the world's largest succulent collections.

An ornate private entrance to the Vienna subway built specifically for the emperor.

This grand manse has been transformed into a museum devoted to one of the founders of Fantastic Realism.

A scandalous Art Nouveau collaboration that set Paris all atwitter at the turn of the century.

The last occupied troglodyte dwellings in England weren't abandoned until the 1960s.