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 small town Romanian cemetery filled with darkly humorous gravestones.

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.

Known locally as the Jungfrutornet, this Medieval tower hides a dark legend.

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.

A Byzantine-era church hidden in a wooded area below the Acropolis.

An abandoned Byzantine fortress and notorious prison.

This gem is often wrongly overshadowed by the larger, newer Metropolis church in Athens.

Where commuters walk through remnants of an ancient Greek necropolis.