A neolithic tomb converted into a tiny chapel.

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

This star-shaped military outpost is now simply trying to protect itself from neglect.

This crumbling Portuguese ruin overlooks the populace it once ruled.

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

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.”

This slumbering beast honors the Bavarian soldiers who died in Greece during a 19th-century typhoid outbreak.

The historic building has preserved human organs, unusual hexagrams, and scars from a political assassination.

The Cycladic architecture makes this Athens neighborhood feel like an island paradise hidden in the shadow of the Acropolis.

The ruined doorway is a portal to the building's turbulent and torturous past.

This small 16th-century church in Athens is almost entirely surrounded by a modern building.

This 15th-century island fortress later served as home to the executioners no one wanted to live near.

An ancient octagonal weather station named for the eight Greek gods of wind.

The ruins of an abandoned medieval city where the last Byzantine emperor was crowned.

This ancient Greek place of assembly and marketplace is being revealed layer by layer below the modern Athens cityscape.

This legendary city has been a tourist attraction for centuries.

This demon atop the Notre-Dame de Paris looks utterly bored.

This ancient Roman bridge and aqueduct still stands as a wonder of classical construction.

This salt marsh in Southern France is as pink as the flamingos that inhabit it.

This iconic Parisian bookstore doubles as the "Tumbleweed Hotel" for traveling writers.