This poured-concrete water reservoir is a gem of modernist architecture well-hidden in a city forest.

This railroad track was so secretive that it was omitted from all maps.

A traveling Bronze Age sacrificial stone that was used to honor elves, fairies, and other woodland spirits.

"Only the dead get off at Kymlinge."

A massive land art sculpture fills a green space once tarnished by a landfill.

Sweden's largest optical telescope sits on a rooftop in Stockholm.

A rare surviving Victorian greenhouse designed specifically to house giant water lilies.

Thousands of coffin-like pillars make up this controversial Holocaust memorial.

Tucked away in a downtown Stockholm park are the remains of a World War II defense position.

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

A surreal statue honoring Prague's favorite literary son.

Steadily reminding Czechia of its past.

A church of bones, decorated with 40,000 human skeletons.

This doorless 20th-century elevator doesn't stop or slow down.

A 400-year-old mummified arm dangles from the ceiling of St. James the Greater, serving as a warning to thieves.

The first museum in the world devoted to sexual gadgetry.

The hidden lair of an alchemist rediscovered in a 2002 flood.

Macabre astrological automaton clock dating to the late 1400s.

A plaque marks the spot where the saint was shoved off the Charles Bridge and into the river.

One of the famous Czech artist's lesser-known Prague installations appears to be a glowing fetus affixed to a drainpipe.

This walkway is so narrow it needs its own light to stop pedestrian traffic jams.

Synagogue built from the stones of Solomon's temple contains the golem of Prague.

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

What looks like a suicide in progress is actually a statue of Sigmund Freud.