An abandoned, deteriorating tuberculosis hospital from the turn of the 20th century.

Colorful and chaotic stacked hotel in North Holland.

An ingenious Dutch land art project uses grass ridges to cut airport noise pollution in half.

This real life asylum of horrors is now an abandoned ruin that hides the unbreakable code to one patient's insanity.

A giant pineapple, a symbol of hospitality, and an amazing vacation rental option.

A subterranean ice warehouse that has lain hidden beneath central London for over a century is now open to the public.

Pop culture has helped to keep this iconic British building from being destroyed.

The largest of London's subterranean rivers and once a mad, bad center of London life.

A hands-off space for graffiti artists to hone and display their skills.

Hidden beneath the streets of London is a secret subway that only carried mail.

London's smallest police station is barely the size of a phone booth.

Kings Cross Station pays tribute to its role in Britain's best-selling book series.

One of Scotland's most important modern structures, it just made the '100 Most Endangered Sites' list.

This castle was established by the 4th Duke of Montrose and is connected to the Buchanan Clan.

These medieval skyscrapers dominate the skyline of this small Tuscan town.

A part of the world's largest marsh seems to be growing bright red Martian grass.

A massive underwater sinkhole made famous by Jacques Cousteau.

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

This giant boulder is pinched over a 1000-meter abyss by two mountains.

A 4,500-year-old forest is slowly being revealed from beneath the sands of a Welsh beach.

This natural Icelandic fissure allows divers to swim right between two volatile tectonic plates.

Each spring, a dreamlike carpet of bluebells overtakes the forest floor.

The mysterious, fantastical woodland inspiration for "The Lord of the Rings."

Giant, friendly pelicans in Central London, the most unlikely of places.