This 17th-century street hidden beneath Edinburgh was once a breeding ground for the black death.

This $3 million model train takes you through Chicago, Seattle, and the thousands of miles in between.

A 19th-century cabin built into a hollowed-out Sequoia tree.

Quite simply the largest tree in the world (by volume).

Four hundred granite steps were built into this massive rock by the National Park Service.

Cleveland's giant "free" stamp is a nod to the Civil War, but was misinterpreted for years.

This weird abode has inspired everything from the "House on Haunted Hill" to a robot hunter's pad.

Ninety feet off the valley floor is an ancient dwelling put under protection of the U.S. government by Teddy Roosevelt.

Built for an exposition in 1915, these horticultural displays have stood the test of time.

Paranormal experiences in this hotel's room 217 led Stephen King to write "The Shining."

This cathedral dedicated to Louis IX, sainted King of France, holds many secrets.

Inspired by a piece of concrete, these three pyramid-shaped buildings have been beloved Indianapolis landmarks for over 50 years.

Allegedly haunted by Walt Disney himself, this inconspicuous lamp is always kept lit in his honor.

A tunnel with windows, so you don't miss out on the impressive views.

A snapshot of the city's fascinating voodoo culture.

The world-record holder for the longest bridge stretching continuously over water.

On Waikīkī Beach, a monument to four extraordinary individuals of dual male and female spirits who brought the healing arts from Tahiti to Hawai'i.

The only royal palace on U.S. soil has been a territorial capitol, a military headquarters, and a prison for a queen.

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

This massive chalk hill carving is one of England's most beloved giant horse geoglyphs.

Frank Lloyd Wright died a year before construction on his largest public project even began.

George Lucas donated this park to honor the birthplace of his two biggest movie franchises.

A massive ultra-modern church presents a science-fiction view of Catholicism's inclusive future.

The sea once considered an ecological wasteland is now called "crown jewel of avian biodiversity" by scientists.