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

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

A series of caves under Castle Hill that once held the prisoner Vlad Tepes, better known as Count Dracula.

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

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

Gaudí's famously flamboyant architectural style is on full display in this sprawling park and garden.

One of Antoni Gaudí's most classic buildings is well-known for its "dragon-back" design.

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.

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

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

It houses the remains of a 17th-century version of the Titanic.

The topiary maze at the Habsburg hunting lodge.

Oldest building in California still in use.

Stripes of flowers bloom each spring in a 50 acre rainbow of color.

This Pringle-shaped ledge makes for the perfect photo op.

This futuristic bridge is one of the longest self-anchored pedestrian bridges in the world.

The classic Atari game's iconic aliens have invaded downtown San Diego.

A sculpture of the famous photograph stands on San Diego's "Greatest Generation Walk."

An inconspicuous footbridge beloved by San Diego locals.