Ruined 11th century abbey built by King David I in Edinburgh, Scotland.

The sign at the garden gate reads: “These Plants Can Kill.”

Banksy gives themself artistic license with this piece of London street art.

This 17th-century street hidden beneath Edinburgh was once a breeding ground for the black death.

An easily overlooked stretch of ornate window fronts and gaslight lamps that could be right from the pages of Dickens.

This astonishingly geometric cave has inspired everyone from Jules Verne to Pink Floyd.

A kaleidoscopic warehouse-maze of handmade neon signs.

The largest self-built castle in the U.S., six decades in the making.

This whimsical group of statues is a favorite of children who love to climb all over Lewis Carroll's beloved characters.

The second-largest cave chamber in the world was discovered in 1898 by a 16-year-old and a friend known as "Pothead."

At this Denver landmark, the meals are compulsory, the sopapillas are complimentary, and the insanity is everywhere.

Take a drunken tour inside the world's largest known geode.

A faux European lane smack dab in downtown L.A.

Collapsing castle on the Hudson river was once the storage site of military surplus business.

An abandoned castle owned and ignored by Masons carries a cursed history.

A three-story copper skybridge connects two Manhattan buildings with Art Deco luxury.

The oldest operating apothecary in the US has treated everyone from Thomas Edison to Mark Twain.

A meditative space out of a fantasy story.

The second oldest continuously operating bar in Louisiana.

A house filled to the brim with oddities and curiosities.

Featuring a casually threatening atmosphere along with dessert and coffee to die for.

Mural made of 100,000 pieces of hand blown glass, and one of the largest glass murals in the US.

This underground oasis is one of North America’s most fascinating prehistoric places—and you can scuba dive in it.

This strange seaside tower got its name from a wealthy eccentric who would hide coins among its stones.