Architectural monsters are devouring this palace's every door and window.

An ossuary built in 1210 to collect bones from the Ospedale Maggiore of Milan.

Geothermal waterfalls in Tuscany.

This 16th-century monastery has been turned into a surrealist architecture compound.

Architectureal fantasy quarter of Rome.

The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."

An Italian crevasse filled with abandoned buildings gives visitors a look at the world without humans.

A secret garden in a picturesque Edinburgh village has inspired artists for centuries.

Ruined 11th century abbey built by King David I in Edinburgh, Scotland.

17th century streets hidden under Edinburgh were once a breeding ground for the black death.

This astonishingly geometric cave has inspired everyone from Jules Verne to Pink Floyd.

This salt marsh in Southern France is as pink as the flamingos that inhabit it.

This French castle is said to have once held the Holy Grail but is now a gorgeous mountaintop ruin.

This historic island prison holds one of the dungeons from the Count of Monte Cristo even though it is a work of fiction.

The mental institution where Van Gogh created some of his most famous work now allows guests to walk in the artist's footsteps.

A Gothic cathedral created from volcanic rocks.

Sacked by Vikings, blessed by William the Conqueror, dealt a fatal blow during the French Revolution—these ruins have seen it all.

This French ghost town from World War II has been left as a memorial to German atrocities during World War II.

This whimsical castle of grottoes was the labor of love of a French postman, and one of the greatest achievements of outsider architecture.

This 1,300 year old monastery built atop a single rock was once only accessible depending on the whims of the tide.

Half-drowned wooden stumps and stone blocks are all that remain of a Victorian landing that was destroyed by storms.

Part museum, part piece of Arthurian-inspired history, this stately hall attracts King Arthur fans from miles away.

London's most popular recording studio, located in the capital's East End, runs partly on solar power and has played host to some of the world's biggest acts.

This ancient bridge made of stone slabs is said to be reserved for the devil to sunbathe.