Buried five stories underground, this Soviet bunker is packed with gas masks and Cold War paraphernalia.

The history of radiation is on safe display at the foot of a radiation science laboratory.

A subterranean shelter remains intact under a busy Paris railway station.

This Parisian café sticks almost exclusively to an ethos of reuse.

This unusual elevator doesn’t stop or slow down.

A floating cat sanctuary on an Amsterdam canal.

This gorgeous reading room houses the oldest and largest art history library in the Netherlands.

This historic Amsterdam bar used to accept sailor's monkeys as payment.

This 22-floor tower's Skydeck offers panoramic views of Amsterdam.

This unattributed sculpture in Amsterdam is hiding in plain sight.

Seven mini rowhouses fill the gap between 54 and 70 Westerstraat.

Some people believe that this makeshift space monitoring station received transmissions from clandestine cosmonauts.

Underneath a chalk hill in France lies what Hitler hoped would be the underground launching base for a devastating new weapon.

An exclusive waiting room built for the royal family in the 1920s is hidden in Milan’s central station.

The signs of a long buried road can still be found hidden beneath a London sewer grate.

This inexpensive lodging house was once a prison notorious for its inhumane practices.

The remains of a paranoid inventor's hidden workshop lie in beautiful ruins amidst a Canadian park.

Canada's subterranean Cold War museum has doubled as a movie set.

Once a train station along the Great Eastern Railway this vibrant coffee shop and bar is where members of London’s creative class mingle.

Banksy gives themself artistic license with this piece of London street art.

On Japan's Tashirojima Island, cats are king.

A rocky sea serpent hides caves, blowholes, and a spectacular natural bridge.

A 30-acre garden inspired by the principles of modern physics.

Pyramid shaped monument with a tall tale attached.