This imposing 20th-century castle was abandoned before it was ever completed.

The coffin-shaped church was once home to monks who slept in coffins.

This symbol of Polish heritage survived the occupation during World War II, hidden in plain sight.

This religious complex carved into a cliff is steeped in legends of miraculous stags and the Holy Grail.

You can still walk across this beautiful medieval bridge in Andorra.

This parody of ecclesiastical cloisters features famous figures from the 20th century.

The world's tallest bridge is also possibly the most elegant.

The world's most famous cheese caves.

Designed to mark the geographical center of France.

The experimental test tracks of a retro-futuristic monorail still stand in the French countryside.

A former milk-delivery driver and his wife turn their home into a glimmering mosaic.

This saucy statue once caused outrage among locals.

This "social palace" housing complex created a relatively stable and self-contained worker's society... for a time.

The shape of this old salt factory complex was inspired by the course of the Sun.

Part of this hotel resides in Switzerland, the other in France, and the border splits the honeymoon suite.

A tiny rural community in Switzerland was home to one of history's most shocking murders, and led to the banning of Absinthe for nearly a century.

This colorful but controversial ceiling has been likened to a 21st-century Sistine Chapel.

An opulent monument built for a duke who donated his entire fortune to the city of Geneva.

The world's largest second-hand graces a clock surrounded by constantly changing flower beds. 

Caves famous for the dragon-slaying saint who lived there.

This historic covered bridge contains a series of macabre paintings that communicate one thing: everyone dies.

The great Danube river starts here.

A former ironworks that was the first UNESCO industrial site.

This work of art, which took 35 years to complete, has a motorway running through it.