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

A semi-scholarly approach to sex.

Elevated freight railway turned wildly successful urban park.

An existential riddle in the world's largest ancient castle.

An eerie, existential museum dedicated to the author of "The Metamorphosis."

A collection of anatomical samples from one of the first anthropologists to suggest that humans reached North America by crossing the Bering Strait.

A bust of Franz Kafka spins in pieces, reflecting the writer's inner torment.

Two stunning 17th-century libraries and a cabinet of curiosities.

For 60 years, the academy had no permanent location until members voted Washington D.C. as its forever home.

This stately mansion, built in 1787 by America's first Secretary of the Navy, is rumored to be one of the most haunted buildings in Washington, DC.

A building shaped like the Army Corps of Engineers logo, because why not?

The only National Monument ever to go missing for nearly 50 years then resurface in a dump.

The monument's pointy aluminum tip has been melted down by repeated lightning strikes.

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

A traveling postal dog covered 48 states and more than 140,000 miles, and he lives on as taxidermy, patched up with a rabbit's foot and a pig's ear.

Seemingly unremarkable items like empty sushi trays, chef hats, and freshness stickers are being preserved so future generations can look back on this beloved cultural import.

An obscure public service from the U.S. government that redeems burnt, moldy, and soiled old greenbacks.

The most decorated dog of World War I is preserved in the Smithsonian.

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

This lonely waterfront memorial to the men of the Titanic was erected by the "Women of America."

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

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

Franciscan monks created a facsimile of the Holy Land for North Americans who couldn’t afford the trip overseas.