A once-luxurious, now abandoned hotel in the Italian Alps.

A hermit's tiny cell built into the cliffside that saved him in South Pembrokeshire.

A 19th-century subterranean reservoir repurposed as a contemporary art cave.

The "world's smallest volcano" has been used to store meals and dispose of dead bodies.

Europe's largest natural bridge has a 19th century royal chateau built into its side.

The signs of a long buried road can still be found hidden beneath a London sewer grate.

Palatial mansion estate used in films including "Flowers in the Attic" and "The Witches of Eastwick."

An eccentric inventor's castle home with its own indoor weather system.

Inspiring Herman Melville and Henry David Thoreau, Mount Greylock in western Massachusetts is the highest point in the state at 3,491 feet above sea level.

The highest point in Maine is a grand gift to the state citizens that also happens to be one end of the Appalachian Trail.

This tiny, painted door at the base of a tree stump has been a fixture of the Harvard University campus for decades.

These towering spires and glowing walls are carefully crafted from hundreds of thousands of icicles.

A 19th century library favored by Edgar Allan Poe and H.P. Lovecraft, known by locals as "the Ath."

A pair of 7-foot legs belonging to the military man of the Mayflower stand jauntily by the side of the road.

This jaw-dropping 19th-century bridge uses its reflection to form what appears to be a perfect circle.

This luxury hotel suite is located deep in the bowels of an old mine.