These relics of the city's past now exist as a prominent modern feature.

Op-art architecture designed for happiness.

A monument dedicated to a lone, brave invader.

A mechanical clock built in 1914, with a rotation of 12 historical figures on its face.

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

Rich with fauna and flora, nature-lovers can walk across the sea at this UNESCO World Heritage spot.

The rock carving that became an internet meme.

The attic of a four-century-old canal house hides a clandestine church.

A beautiful bronze statue of the greatest fossil hunter of the 19th century.

Wooden sleds have replaced donkeys to cart goods around this utterly charming car-free village.

This strategic isle was once swapped between empires and almost entirely destroyed in a bomb explosion.

One of the most spectacular bridges in Spain spans a narrow chasm that divides the city of Ronda.

Rare karst landscape eroded from a flat seabed.

Single runway interrupted by a busy road that cuts across its middle.

This psychedelic tourist trap is a leisurely descent into madness.

On the highest peak in the Harz Mountains, science and the occult faced off in a failed attempt to turn a goat into a boy.

When a medieval fire claimed the original St. Stephen’s Cathedral, it sparked a pattern of unquenchable organ building.

This striking royal residence is the largest Renaissance-style castle in Scandinavia.

Model Trains and Much More in Hamburg.

The last bastion of Roman presence north of the Alps looms over a German town.

Twisted buildings adorn the banks of the Rhine river.

During the Soviet era, the spire of this longstanding church was used as a radio transmission tower.

Housing the famous Norwegian ice-defying 19th century polar exploration ship.

The first recognized Neanderthal remains were found in this now-lost cave in 1856.