A marvel of Byzantine engineering under the streets of Istanbul.

A Swiss amusement park entirely dedicated to the theory of ancient astronauts.

Traversing steep Alpine slopes, this engineering marvel is one of the longest and highest funiculars in the world.

The second-highest train station in Europe.

A cablecar-station-turned-revolving restaurant with 360-degree views of the Swiss skyline.

A historic observatory precariously perched at the "Top of Europe."

This strange statue features a bust of the famous composer plopped atop a woman's body.

This 19th century cyclorama acts like an analogue time machine to a different era.

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

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

The topiary maze at the Habsburg hunting lodge.

This Slovak bridge is known both for its connection to a national uprising and its UFO-shaped eatery.

A two-way chairlift system between Zugliget and the highest point in the city.

The mummified right fist of a 1,000-year-old saint-king sits inside an ornate golden reliquary.

A Trabant car, a kangaroo statue, and a plethora of plants take over this abandoned-factory-turned-bar.

From Austrians to Nazis to Soviets, this historic Budapest fortress has a history as complex as the city itself.

Built in 1870 at the bridge that connected Buda and Pest, this spectacular incline railway was almost lost forever during World War II.

Once the home of a hermetic monk, this cave now houses a small church.

A trail of iron footwear stands as a monument to the thousands executed along this riverbank during WWII.

Where commuters walk through remnants of an ancient Greek necropolis.

The ruins of this medieval castle in Northern Ireland have inspired artists from C.S. Lewis to Led Zeppelin.

A meandering boardwalk across the bogland leads to a "stairway to heaven" with sublime views.

This short bridge is the only thing connecting a tiny Irish island to the mainland.

Northern Ireland's Brobdingnagian stepping stones.