The largest of Denmark's seven mysterious round churches stands on an island in the Baltic Sea.

World War II Soviet Russian soldiers were buried on the Danish island after the war had ended.

Northern Europe’s largest castle ruins sit precariously on an island cliffside.

Once a granite mine, this beautiful lake is the perfect place to cliff jump and zipline in Denmark

Local legend says a monk brought Christianity to Bornholm through his sermons in a cave inside this free-standing rock.

Hitler's bleak vision of relaxation still stands as a mostly abandoned 10,000-room resort complex.

A Belgian self-built tower inspired by the Bible and ancient civilizations.

What once sat in the world’s spotlight is today a largely disused ghost complex.

After a catastrophic forest fire, a Greek artist transformed scorched tree trunks outside an old sanatorium into this haunting sculpture garden.

According to legend, this cavern holds the passage that Persephone used to travel to and from the underworld.

Only open for two days a year, this church links ancient Greek and modern Christian celebrations.

This historic structure has been used as a mosque, a barracks, a prison, a school, and a bakery.

This striking sculpture of Icarus honors Greece's fallen flyers.

An ancient Greek monument and a Byzantine church coexist inside this cave.

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

Legend says this sacred tree was a gift from goddess Athena.

The approximate spot where the last Grand Master of the Knights Templar was put to death.

The narrowest street in Paris.

This cobblestoned medieval-style town was entirely constructed in the 1990s and 2000s.

The standard measure of Lagom, a measure of what is enough.

These ancient rune stones plucked from the countryside now call this university park home.

The marker that allows students all over the world to be late for class.

A modern, secular take on a traditional Virgin Mary motif.

Legend has it that this church faced a troll problem, leading to the affixing of a stone face of Satan above the entrance to deter further encounters.