Sweden's first nuclear reactor, R1, can be visited 25 meters underground.

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

Masterful ceramic fountain and map of the Pacific Basin.

Join the circus for a few lessons to learn clowning, acrobatics, and Chinese contortion.

Barely visible foundations remain where Stow Lake’s “observatory” once welcomed visitors.

A still functioning vaudeville carousel that has operated for over a century boasts a colorful menagerie and past.

The remains of a ruined mansion memorialize the 1906 earthquake.

A favorite haunt of dinosaur loving children and hallucinogen loving hippies alike.

An artsy hidden staircase leads to breathtaking views of San Francisco.

Ice cream stand, snack bar, and time capsule of milk conveyance.

The Boston square dedicated to the dark poet who was born nearby.

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

Two thousand artifacts from around the world collected by one woman who loved to travel.

A beautiful Victorian-era cemetery, complete with a miniature village.

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

Week-long block party becomes a competition for the best decorated street.

A beautiful but toxic fountain of mercury.

Despite having a dome made of papier-mâché this tiny observatory has survived for over a century.

An abandoned nightclub has become a vibrant work of art.

A well-preserved medieval village nested on a rocky outcrop and surrounded by a network of cliffs, natural bridges and canyons.

Bordered by forest on three sides and the ocean on the other, the Great Dune of Pilat is the highest sand dune in Europe.

From carts to cars, this leftover Roman bridge in France has managed to survive for centuries.

Resting on a hill overlooking the coast, these medieval ruins look completely deserted save for their restored chapel.

Personal garden filled with mosaics made of recycled garbage.