A master of trompe-l'oeil creates a stunning, tourist-fooling dome out of a flat ceiling.

A detailed pachyderm supports Rome's smallest Egyptian obelisk.

This gallery commissioned by Cardinal Spada is known for its magnificent optical illusion.

A mysterious chasm in the heart of the ancient Roman Forum, the Lacus Curtius was once believed to be a gateway to hell.

A 130-year-old urinal is the oldest of Stockholm and perhaps all of Sweden.

Stockholm's narrowest alley is barely over two feet wide.

Buried beneath an unassuming Gotland farm was the largest collection of Viking silver, mostly of Islamic origin.

A countryside Romanian cemetery filled with colorful crosses bearing lyrical, ironic, or satirical rhymes.

This towering church is home to a world-famous organ and a treasure trove of medieval art.

The works of poetry's biggest names grace the walls of the city of Leiden, all carefully painted by hand.

Lumps of significant stone from around the world surround a flaming monument for peace.

Legend says this fabled well held part of a mythical Norse tree.

The official meeting point for the oddly named governing assembly of ancient Sweden.

This mysterious runestone embedded in a church wall is linked to the medieval cult of Saint Erik.

Ancient burial grounds of the wealthy.

This trio of stone spires claims to be the only preserved medieval execution site in Europe.

Sweden's oldest street has not changed for nearly a millennium.

Largest island in the Baltic Sea experiences such idyllic weather that roses bloom in the middle of December.

This grisly exhibit houses skeletons and weapons from a devastating 14th-century clash.

It is said that each of the white stones in the red facade of this medieval house represents the head of a murdered Swedish noble.

An ancient Viking runestone hidden in plain view in Stockholm's old town.

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

It houses the remains of a 17th-century version of the Titanic.

Stockholm's decidedly unique public transit system has doubled as the world's longest art gallery for decades.