This massive concrete sculpture is said to be the heaviest communist monument on Earth.

This tiny Bulgarian town offers a stunning location in the mountains and a storied history.

An architectural marvel that spans the Arda River, and has stories of a haunted past.

This futuristic German television spire is actually the world's largest digital clock.

A giant bug impaled on a 75-foot-tall needle.

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

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

An abandoned saucer-shaped monument in the Bulgarian mountains.

A marvel of Byzantine engineering under the streets of Istanbul.

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.

Macabre astrological automaton clock dating to the late 1400s.

A Dutch passageway's artistic, aquatic-themed makeover pays tribute to the capital city's famed waterways.