This 11th-century castle sits so low you can't see it behind the surrounding buildings.

Unknown to many, this is where items not displayed in a Dutch history of science museum are held.

Outside a Viking museum sits a modern-day runestone made by a Swedish runemaster using traditional methods.

The world's largest underground iron ore mine.

A striking memorial to the Jews of Leiden who were murdered during World War II is scattered throughout the city.

When this 18th-century observatory's meridian was moved, it set Sweden's time back by 0.04 seconds.

This irregularly shaped sea fortress has defended not one but three different sovereign states.

Finland's oldest astronomical observatory once played a crucial role in seafaring and timekeeping.

Finland's northernmost zoo is home to the country's only polar bears.

Roughly 17 million letters to Santa have found their way to this Arctic Circle post office.

This statue and park honor the Swedish chemist Jacob Berzelius, one of the founders of modern chemistry.

Legend says a giant, venomous spider once dwelled within this Polish church.

A menacing statue of this mythical creature can be seen at the legendary site of the monster's lair.

This biographical museum honors the groundbreaking scientist at her birthplace in Warsaw.

A Japanese video game arcade hides in the back of a Swedish pool hall.

This bell stars in a tragic love tale and is said to make wishes come true.

Once a black market electronics marketplace, now an otaku shopper's paradise.

After a profound show of devotion for his master, a dog becomes the symbol of loyalty for an entire nation.

The Polish capital has had a deep connection to its guardian mermaid for almost a millennium now.

Walk upon the mementos of the dead in this Parisian courtyard paved with medieval tombstones.

This ornate Victorian marketplace was the setting for Diagon Alley and the Leaky Cauldron in the first ‘Harry Potter’ film.

This enormous 32-foot painting depicts Poland's greatest medieval battle in glorious detail.

Special benches that play Chopin's music are scattered throughout his native city.

In the summer, the area around this sculpture transforms into a vibrant concert venue.