A perfectly circular lake is formed by the crater of an ancient underwater volcano.

This abandoned five-star hotel is now a five-star urban exploration destination.

This restored Portuguese cafe may well be the most beautiful place in the world to grab a Big Mac.

One of the largest Roman settlements in Portugal.

This unreal Portuguese palace looks as though it's made from a pile of different castles.

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

Elaborately carved to showcase the glorious wealth that the age of exploration brought to the Portuguese empire.

The stunning interior of this Gothic church is covered in ornate gold details.

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

An ancient and majestic fortress that played an integral role in Portugal's road to independence.

Legacy of the earthquake that nearly wiped Lisbon off the face of the Earth.

Commonly acknowledged as the only public monument to the Devil himself.

Madrid's romantically ornate crystal palace has been offering shelter to plants and art for over a century.

Swedish skyscraper with a 90° twist.

From Ancient Rome to WWII, Neupfarrplatz has over 2,000 years of history underneath its main square.

The stones of this formerly witch-obsessed castle were used to build a church.

This abandoned coliseum was intended to be a grand Nazi rallying ground before it was halted at the end of the war.

A castle from the Holy Roman Empire that hosts traveling youth... in its stables.

This chimerical bridge/tunnel appears to dead end right into the sea.

Sweden's "good old days" painstakingly re-created in a model village.

Golden cobblestones remember a time when this small alley was used to avoid having to give a Nazi salute.

These bronze pamphlets remember a remarkable group of Germans who fearlessly opposed the Nazis in the very center of their power.

Explore the complex ecology of this multifaceted nature preserve by riverboat.

What was once thought to be a wellspring of unicorn bones is actually just a prehistoric burial site.