Around 100,000 bodies are buried below the medieval headstones, many of which mark graves with multiple bodies stacked up to 12 deep.

Macabre astrological automaton clock dating to the late 1400s.

This coastal cavern is associated with the Hawaiian god of creation.

An authentic replica of an Asian temple and garden hidden amongst the natural beauty of Hawai'i.

Wander among the gravestones in this historic border town.

An abandoned tank sits in an empty London lot as a symbolic middle finger to local city planners.

This massive collection of British military artifacts includes the heartbreaking personal letters of the men in the trenches of WWI.

One of nature's most well-scheduled phenomenons resides in Wyoming's Yellowstone National Park.

A beautiful geyser under environmental threat.

An architect's childhood fantasy treehouse made real.

The largest hot spring in the United States is, as the name suggests, a stunning show of natural color.

The last physical evidence of the Lewis and Clark trail is one of their autographs etched into this giant rock.

A Spanish-style estate that has traded black ties for rock concerts.

A focal point of the Cuban government, this city square features one of the most iconic images in the country.

A cavernous three-story, 43,800-square-foot basement that was forgotten about for 60 years.

The remains of Martha, the last known passenger pigeon, serve as a tool to educate about conservation.

The only Leonardo Da Vinci painting in the Western Hemisphere.

A little marble compass above George Washington's (empty) tomb in the Capitol marks where D.C.'s four quadrants intersect.

Corn-inthian columns with a uniquely American take on neoclassical architecture.

One of the three perfect vellum copies of this historic book known to exist is on display in a specially-designed case.

The 72-foot giant escaped confinement in a large patch of mulch only to be reburied in the sandy shores of the Potomac River.

This rare triple-jurisdiction drawbridge passes through Virginia, Maryland, and Washington, D.C.

A massive, majestic mammal watches over pedestrians from his perch atop a former B.P.O.E. lodge.

The final resting place of an unidentified revolutionary soldier sits behind a Virginia church.