The largest stone circle in the world has ended up bringing up more questions than it has answered.

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

The Hudson River School comes alive at this palatial estate.

The hidden "ballroom" under a mansion lake was built by a criminal who ate a cyanide pill during his trial.

Hidden behind a wall for decades, this masonic lodge was only rediscovered during renovations.

An unsettling painting of three faceless sisters that is surrounded by history and legend.

Medicinal spa created with the discharge from a geothermal energy plant.

An ethereal glowing blue ocean cave in Croatia.

An odd little fishing town that is inundated by tourists looking to be locked up in a cage and surrounded by great white sharks, because why not?

An underwater city for the dead.

This "thrice-cursed" island is allegedly home to Captain Kidd's lost treasure.

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

Reclaimed by nature, the ruins of Doodletown, New York are remnants of a town consumed by a state park.

Island where motor vehicles are banned -- home to the only carless highway in the United States.

What was once a unique system of urban elevators is turning into a mechanical ruin.

A stunning, two-tiered waterfall made famous by poets, artists and the legend of a ghost dog.

An island in the middle of a lake, in the middle of a volcano, in the middle of a bigger lake, in the middle of a bigger island, in an archipelago, in the Pacific Ocean.

An Australian lake whose pink hue defies scientific explanation.

A lake in the middle of the tundra of Quebec is said to be the purest freshwater lake on Earth.

Submerged trees jut ghost-like out of an idyllic turquoise mountain lake.

These remote Florida islands have a history of sea turtles and sunken treasures, and one of the world's largest coastal brick fortresses.

The old Niles Canyon Aqueduct in the San Francisco Bay Area is a bemusing and secret trail through nature for wayward travelers.

Home to the infamous "Typhoid Mary" and the worst loss of life in New York's history prior to September 11, 2001.

They squeal, they nosh, they look like predators.