A small marionette collection located within the dark cellars of an 11th-century Austrian castle.

This outsider art house has gone from clinical creation to astounding artwork.

Baroque celebration of the end of the Great Plague of Vienna.

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

Unfortunately, you can no longer spend a night in this single-person treetop hotel.

Sweden's southernmost point is located in this charming fishing village.

Stockholm's deepest subway station is also a stunning ecological wonder.

A peace symbol in Northern Ireland is among the world's largest hedge mazes.

The only medieval bridge in Britain with its defensive tower still in tact.

Teeny tiny hotel on the coast of the Canary Islands.

Medieval ruins nestled within a breathtaking swath of Spanish nature.

An ancient tower built during Roman times as a lookout post still stands to this day.

To fit bodies into this Renaissance crypt, they were first left to decompose in the crypt's rotting room.

The quirky - and private - constructions of a secluded artist depict the house of God.

This monumental gateway marks the northern edge of Brighton and is a welcome sign to all visitors to the seaside city.

An ancient water supply dating back almost 500 years can still be found standing in East Sussex.

A tiny chapel perched along a 14th-century bridge.

Where the rules of that most quintessentially English game were first devised by an eccentric inventor.

The second-longest pier in the U.K. stretches a whole kilometer into the Irish Sea.

Bask in the 19th century grandeur of an eccentric Freemason millionaire's private gardens.

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.

One artist's collection of homemade handicrafts doubles as a monument to 20th-century material culture.

Inside this chapel, Victorian jailers took the separate system to new levels.

A hidden three-foot-wide house separates these two regal churches.