A creepy sculpture of a decapitated head invites viewers to see St. Louis through its empty eyes.

An enchanting monastery in the Spanish countryside appears lifted from a fantasy tale.

This wrecked airplane has been sitting on a black sand beach since the 1970s.

A 16th-century Andalusian palace.

This former charity hospital for elderly clergy houses some of Seville’s most treasured paintings.

The final resting place of the great navigator, or maybe his brother.

The Roman Emperor's lost summer home and grotto full of enormous sculptures sit along the Italian seashore.

These Egyptian statues have survived for 3,400 years and were an acoustic wonder of the ancient world.

Centuries-old bridges grown from tangled roots.

Thousands of exquisitely carved stone water storage wells, hundreds of stone steps fill this exquisite medieval stepwell.

A spiritual sanctuary in a natural cave.

This hulking behemoth is actually five interconnected towers built in the 1960s.

The former locus of Boston's high culture has been shuttered and buried for over 70 years.

The oldest Italian café in Boston, this spot also serves as a veritable museum of vintage coffee ephemera.

A morbid secret lies hidden within the beautiful walls of the Boston Athenaeum.

19th-century operating theatre in which the use of ether was first demonstrated - plus, a skeleton and a mummy!

This Boston medical museum features the skull of the famous medical case of Phineas Gage.

Ice cream stand, snack bar, and time capsule of milk conveyance.

The history of the tea trade is told in bas-relief on this historic pair of Boston doors.

The often-overlooked ruins of one of the first buildings designed by famous landscape architect Frederick Olmsted.

This upscale streetwear store is hidden behind a fake Snapple machine in the back of a deli.

This abandoned Brutalist treehouse is a hidden architectural relic.