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

One part local history, 99 parts gruesome haunted house.

This 4,000-foot-diameter hole is touted as "the most well known, best preserved meteorite crater on Earth."

The first declared National Monument in the United States.

This former coal gasification plant found a curious second life as a popular public park.

The gorgeous library at Trinity College is home to remarkable treasures of Irish identity.

One of the Seven Wonders of the Modern World holds the world's tallest metal staircase.

The site of the climactic scene from the classic horror film is now a historic landmark.

An historic and oft-filmed spot for musclebound iron pumpers on the Pacific coast.

The American Revolution was galvanized into serious action due to the tragic clash with British soldiers that occurred at this location.

Macabre headstones carved with winged skulls, dancing skeletons, and pithy reminders of impending death.

Home to items never before seen by the public.

One of the tallest buildings in Iceland, and perhaps, the most visually impressive.

The oldest cemetery in New Orleans, resting peacefully for over 200 years now.

An "inside out" building in the historical center of Paris, featuring Europe’s largest modern art museum.

Eighty million natural history specimens call this gargantuan museum home.

The last remaining relic of San Francisco's glittering 1915 Panama Pacific Exposition.

A museum dedicated to the history and exploration of both popular music and science fiction.

A giant Troll lurks under one of Seattle's oldest bridges.

Macabre astrological automaton clock dating to the late 1400s.

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.

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

Dim sum, served in a grand old theater.

The Boston square dedicated to the dark poet who was born nearby.