A chain of 16 wondrous lakes formed as a result of the gradual dissolution of soluble layers of bedrock.

Yugoslavia's biggest underground airport lies in ruins.

A musical instrument played by the sea.

This 135-year-old weather station studied the effects of the climate on human health.

An eclectic art form practiced by untrained masters is celebrated at this museum in the heart of Zagreb's old Upper Town.

All of Thailand's architectural landmarks, plus some made up ones, all viewable via two-seater bicycle.

This 23-foot-tall bear stands amid the hustle and bustle of Hamad International Airport.

This 14th century castle withstood years of battle but is now sliding off the hills into the Danube.

Stone age urban planning.

A giant portrait of an ancient king looms over the river.

A Roman monument to their own civil engineering prowess.

An old spa town in the mountains of Romania where, according to legend, the great hero Hercules once bathed.

This Bronze Age tomb is the centerpiece of a clearing within a beautiful Irish forest.

Monasteries on rock pillars, once accessible only by frayed ropes.

These abundant, over-the-top monuments are so widely scattered that they define the entire compact capital cityscape, often leading to jokes about whether there are more statues than residents.

In the hometown of the Catholic saint and Nobel Peace Prize winner, a memorial dedicated to her legacy.

A muddy alien landscape that is home to rare species of exotic plants.

This automated sculpture of two men peeing will spell out text messages with their micturition.

A plaque marks the spot where the saint was shoved off the Charles Bridge and into the river.

A bust of Franz Kafka spins in pieces, reflecting the writer's inner torment.

A bus with a butt and biceps to put Olympic athletes to shame.

Also known as the Blue Church, the building was consecrated to the daughter of Andrew II.

The largest brick bridge in the world.

This giant glowing "beanpole" adds much-needed pops of color to an otherwise drab power plant.