From bench to vandalism to art, this silly prank seat was funny enough to become permanent.

The oldest playground in America.

The 1920s child prodigy author was last seen here at her Brookline home before vanishing at age 25.

This Dutch-styled residential building was originally a cocoa company's World's Fair showpiece.

Radical Bookstore and Community Space.

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

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

A unique music museum housed in a historic Boston theater.

The final resting place of the first documented Chinese person in the United States lies in a Boston cemetery.

A crumbling hospital from the 1850s on Roosevelt Island.

Just your average Marie Antoinette–themed speakeasy in an abandoned 19th-century subway tunnel.

This red-eyed chrome beast pays homage to the popular modern myth of West Virginia's insectoid monster.

This Cape Cod museum exhibits what it claims is the only authenticated pirate treasure in the world.

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

Down a cobblestone alleyway is a museum dedicated to Romanticism, with a secret garden.

Inside a former cabaret, seven floors of erotic art.

This massive library holds what was once the largest book collection in the world.

A museum on the history of Paris, including a set of Napoleon's toiletries, Proust's room, and relics of the Revolution.

A museum dedicated to one of Paris’s most famous residents, tucked into a corner of one of the city’s most famous squares.

The headless bodies of more than 1,300 guillotined victims of the Reign of Terror are buried here in mass graves.

This lesser-known Frank Gehry building houses a treasure trove of cinema history.

One of the oldest medical collections in Europe focusing on rare surgical instruments.

High atop the Eiffel Tower is a small apartment built exclusively to entertain the science elite and make the rest of Paris jealous.

Former hunting lodge of a duke who was an avid collector of impressionist works.