Apartment complexes built into huge repurposed natural gas tanks.

Vienna's giant wonder wheel had a starring role in one of the greatest noir movies of all time.

The Habsburgs' royal collections of art and wonders.

Op-art architecture designed for happiness.

Built to give thanks for the passing of a plague epidemic, this cathedral is a one-of-a-kind architectural hybrid.

The topiary maze at the Habsburg hunting lodge.

An "inside out" building in the historical center of Paris, featuring Europe’s largest modern art museum.

The ruins of a megalithic monument sit right in the garden of a luxurious Maltese resort.

Trick water gardens from 1619 featuring a 200 piece mechanical theater powered by water.

The oldest garden in Prague, once part of an medieval orchard.

This walkway is so narrow it needs its own light to stop pedestrian traffic jams.

Around 100,000 bodies are buried below the medieval headstones, many of which mark graves with multiple bodies stacked up to 12 deep.

A surreal statue honoring Prague's favorite literary son.

This tipsy office building in downtown Prague was originally called “Fred and Ginger.”

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

A mocking tribute to the past and modern leadership of Prague.

A king's pet, a pope's gift, an artist's inspiration, and a tragic shipwreck.

This Industrial Age architectural and engineering gem helps visitors and residents alike traverse Lisbon, “The City of Seven Hills.”

The only museum with its curator—and her pets—buried inside.

Two stone columns flank the grand Venice square, but there were supposed to be three.

Go inside to really appreciate this 500-year-old technological masterpiece.

A new sculpture calls attention to climate change in the centuries-old city it threatens.

This Venice bookstore has resigned itself to constant flooding by keeping its books in bathtubs and boats.

The world's oldest grape-producing vine has survived four centuries of turmoil and even has its own anthem.