These historic defenses ensured the city within would survive hundreds of years of occupations, sieges, and invasions.

This virtually windowless mass of smooth concrete is the only Catholic church in the city.

A curious cave church carved into the face of a cliff.

Climb inside an iron crystal magnified 165 billion times its normal size.

This legendary giant, born from vegetables, terrorized townspeople and cheated local children in games.

This statue dedicated to the story of a Flemish boy and his dog was relatively obscure in Belgium, but a cult sensation in Japan.

The patron of this extravagant Art Nouveau confection insisted that nothing less than a boat should project from its facade.

Dedicated to the untimely death of American balloonist and parachutist.

This extinct volcano rises above Edinburgh and is special for its panoramic views over the city.

In the waters outside Helsinki, a tiny island once used as a military outpost now welcomes visitors.

Atop this library is one of the most beautiful green spaces in Warsaw.

Walk along the medieval fortifications that have been protecting Tallinn since the 14th century.

These enormous, stern-faced statues greet visitors with lanterns, and sometimes costumes.

One of Jeff Koons’s largest sculptures and his first commemorative work.

This now-defunct synthetic fuel plant was once a major cog in the Nazi war machine.

One of the largest refracting telescopes in the world, and the first built specifically for studying astrophysics.

A medieval setting reimagined into a unique art alley.

Built in the Soviet era, this cableway system still runs gondolas from Odessa down to Otrada Beach.

An exquisite Baroque church in Vienna's old town.

A unique sculpture calls the outside of this steakhouse home.

Countless stories attempt to explain Poland's mysterious J-shaped trees.

Along the edge of this fountain are 365 smaller fountains that represent the days of the year.

Designed as a reminder of one of the darkest moments in Austrian history.

This former insane asylum now holds a pathological anatomy museum.