One of the last few places in Manhattan that employed a pneumatic systemic keeps it on display.

The beautiful tunnel that ran from the lobby to Penn Station is still hidden underneath 34th Street.

A pedestrian island in the middle of world-famous Times Square emits a strange (and purposeful) humming noise.

Granny Smiths and Fujis can both be traced back to Kazakhstan, where apples still grow wild.

Swedish mice can dine at the Nuts of Life restaurant or take a date to the amousement park.

From Coke II to Google Glass, this exhibit features some of the most spectacular commercial flops.

America's oldest Eastern European synagogue provided the immigrants of crowded Lower East Side tenements a space of sanctuary.

A scale model of Russia so big visitors are offered binoculars to rent so they can see the whole thing.

The pits used to load the nuclear bombs onto the aircraft that dropped them over Hiroshima and Nagasaki at the end of World War II.

One of the largest-ever mental hospitals now sits abandoned, surrounded by 25,000 unmarked graves.

The architect of this fanciful complex called it an "oasis for humanity and nature in a sea of rational houses."

A bike being "eaten" by a tree is the real Vashon legend behind popular children's book, "Red Ranger Came Calling."

A little piece of the Shire is hidden behind a plant nursery in Port Orchard, Washington.

Eclectic collections, artwork, and some feline friends fill the writer's former home.

The United States Capitol's former columns still stand.

The walls of the iconic dome are hollow and have a secret stairway.

Members of Congress have traveled between the buildings on Capitol Hill for a century hidden from tourists, press, and storm clouds.

The elevator that makes it possible to fly American flags in bulk over the U.S. Capitol

"Congress may voluntarily remain in session throughout the summer, in order that our Congressmen may be protected from the intolerable discomforts and dangers of the ordinary outdoor weather!”

A nostalgic bibliographic gem.

A hidden gem on the lawn of the U.S. Capitol Building designed by landscape architect Frederick Law Olmsted.

Enormous piles of historically significant stones, dumped by Congress in a forest, and abandoned for 60 years.

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.