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

This eccentrically decorated palace is replete with grottoes, fountains, tunnels, and caves.

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

Elaborate tile work in this railway station tells the story of Portugal.

A stunning 18th-century site where pilgrims ascend by a series of punishing stairs only to return via funicular.

Five sultans and their families rest in eternal splendor, teeming with overlooked beauty and drama.

1513 Turkish world map, full of European state secrets and snarky commentary.

The deepest underground city in Turkey was designed to protect 20,000 people behind massive stone doors.

In this historic region, homes and churches are carved into ancient volcanic rock formations.

Roman ruins top white travertine terraces formed by ancient hot springs.

World's largest bell sits on the grounds of the Kremlin in Moscow.

Hidden in a metro shop under a shopping mall, this small museum tells the story of one of the world's largest urban transit systems.

This newly renovated Soviet-era outdoor exhibition center is bigger than the principality of Monaco.

Gargantuan home of Russian science.

A model village fit for an emperor.

An 18th century wonder of the world, lost in WWII, re-created at the Catherine Palace.

A 250-year-old timepiece-automaton adorned with golden mechanical birds, which still sing to this day.

A subterranean house of worship carved right out of the bedrock.

An abstract monument to a symphonic composer.