This massive underground salt mine now holds a sci-fi theme park in its depths.

Retirement home for giant obsolete machines.

This unattributed sculpture in Amsterdam is hiding in plain sight.

A castle hand-built by a Spanish dreamer in the Australian tropical jungle.

This "floating island" plateau sits 7,671 feet above the forest floor.

Rent out a glass igloo to watch the Northern Lights like you live in the future.

This "floating railway" is one of the world's oldest monorail systems.

This odd Chilean waterfall-cano hotel must be entered via a rope bridge.

The remains of diamond fever taken over by the desert.

Perfectly preserved ancient monastery in an impossibly dramatic location on a rocky island in the Atlantic.

An architectural marvel that spans the Arda River, and has stories of a haunted past.

Cold storage for agricultural biodiversity.

An island filled with hundreds of hanging, decomposing, decapitated dolls.

Hidden in a secluded Greek cove is a pristine beach marred only by the rusting smuggler's hulk stranded on its shores.

Moss and stone turn this waterfall into an otherworldly liquid veil.

A 300-yard long natural tunnel runs through a ridge deep in the Appalachian Mountains.

This lake in the Cascades lives up to its name, disappearing down a hole every spring.

Geothermal waterfalls in Tuscany.

Every autumn, this hillside is ablaze with red summer cypress.

Hot springs monkey spa in the middle of Hell's Valley.

This abandoned fishing settlement may well be the greenest village in the world.

An ancient stone fortress considered by many to be the eighth wonder of the world.

This scalding hot river was thought to be a myth until one geoscientist made it his quest to study the mystical waters.

This red lake 4,000 meters above sea level is home to rare flamingos.