The former locus of Boston's high culture has been shuttered and buried for over 70 years.

This upscale streetwear store is hidden behind a fake Snapple machine in the back of a deli.

An enormous, inside-out glass globe built in 1935.

The oldest building in the District of Columbia was preserved because of a mistaken connection to George Washington.

This unacceptably tall building was the real reason for Washington, D.C.'s skyscraper ban.

A hoard of sky catalogs, astrophysical journals, even the works of Galileo and Copernicus.

There’s a hidden military meme engraved on the World War II Memorial.

The winding route passes through an enclosed alleyway, two tunnels, and leads to the White House basement.

An atomic bomb-proof strongbox protects the U.S. Constitution from terrorists and thieves.

The house where John Wilkes Booth conspired with his co-conspirators.

A nostalgic bibliographic gem.

A painfully obvious spy house sits right across the street from the Russian Embassy.

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

A tiny piece of the Moon is embedded in this stained glass masterpiece.

Home to items never before seen by the public.

A museum and shop on Bourbon Street located in the former home of the second Voodoo Queen of New Orleans.

A 200-year-old bar in the historic French Quarter refuses to give up its place in history, nor its role in securing ours.

Stockholm's decidedly unique public transit system has doubled as the world's longest art gallery for decades.

A snapshot of the city's fascinating voodoo culture.

The world's largest clay lick, where parrots gather to snack.

Sleep in a glass pod dangling off a cliff.

Extraordinary rock formations in open Peruvian fields.

A French artist's vague warning hangs over Belleville.

This off-limits room in the National Library of France is home to a system of pneumatic tubes, once used to bring books to readers.