A floating cat sanctuary on an Amsterdam canal.

The ruins of an 11th-century Norman castle with a rare, perfectly circular shape.

The oldest stone house in Paris was built by its most famous alchemist.

Off-limits and full of venomous pit vipers, Brazil’s Snake Island has a frighteningly apt nickname.

Monty Python fans will recognize this abandoned mine as the Cave of the Killer Rabbit of Caerbannog.

This cave system allegedly holds the "metallic library" of a lost ancient civilization.

A clerical error gave rise to this imaginary micronation in the southwestern corner of Estonia.

In this truly magical place, rent hasn't been raised since the year 1520.

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

Aged nearly 1,700 years, the world's oldest bottle of wine is probably still drinkable.

An immersive environment that is part haunted house, part choose-your-own-adventure, and part jungle gym.

This 170-year-old Swiss guesthouse built into the side of a mountain is best accessed by a cable car.

Isolated atop this Balinese sea crag is a lovely Hindu temple that is said to be guarded by sea snakes.

Two ancient Buddhist temples crown this dramatic rocky pinnacle.

Possibly the smallest church in the world floats in the middle of a pond.

The "Bridge Over the Atlantic" lets you cross the waterway in mere seconds.

An engineering error ensured this cavernous 350-foot-long subterranean thoroughfare was never used as intended.

Constructed during the 7th century this is one of the oldest largely intact Christian churches in England.

The oldest residential street in Europe also features an optical illusion.

This overlooked street light once served as a KGB dead letter box.

The land is full of geologic eye candy, such as otherworldly spires, mushroom-shaped hoodoos, and prehistoric fossils.

One of the most well-preserved castles in Italy also contains a rare medieval example of a port fortification.

This vast, pristine wilderness is home to a rare subspecies of black bear.

On the Oregon coast there is a natural hole that seems to be draining the sea.