"Portugal's Stonehenge" is made up of nut-like stones aligned with the heavens.

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

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

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

There was a top secret plan during World War II to seal a group of soldiers inside the rock.

Single runway interrupted by a busy road that cuts across its middle.

An eerie collection of the surviving structures from a past celebration of the future.

This former charity hospital for elderly clergy houses some of Seville’s most treasured paintings.

Hidden behind a wall, Spanish nuns distribute their signature sweets on a revolving tray.

The world's largest wooden structure.

This hauntingly beautiful cemetery outside a medieval citadel is full of winding paths and ivy-covered graves.

Nine centuries-old fortresses guard the walls of this medieval Romanian city.

A fire once nearly devoured this gorgeous 14th-century Gothic cathedral.

This snug medieval lane is one of the narrowest streets in the world.

The European towns of Brașov and Râșnov each have proud signs reminiscent of the Hollywood sign.

This memorial to the victims of the Romanian Revolution of 1989 is often compared to a potato on a skewer.

Romania's triumphal arch looks out over Bucharest.

This communist behemoth is the heaviest building in the world and a legacy of a brutal regime.

The bust of Romania’s most notorious ruler, Vlad Dracula aka "Vlad the Impaler," keeps watch over the ruins of his medieval court.

The possible imprisonment of Vlad the Impaler here earned the medieval castle its nickname, "Dracula's Castle."

A cablecar-station-turned-revolving restaurant with 360-degree views of the Swiss skyline.

A historic observatory precariously perched at the "Top of Europe."

This historic covered bridge contains a series of macabre paintings that communicate one thing: everyone dies.

This memorial commemorating fallen Swiss Guards of the French Revolution has been called the saddest stone in the world.