A prehistoric geological oddity tucked behind Stockholm's natural history museum.

The library's graceful rotunda is like a bibliophile's temple.

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

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

These 18th-century paintings of Warsaw were used to reconstruct the city after World War II.

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

The composer known as the "Swedish Mozart" arranged to be buried in an unusual spot.

The final resting place of the man whose name has become synonymous with greatness.

Now a hotel, this former bank was the site of a robbery that spawned a psychological phenomenon.

A heated statue pays tribute to one of Sweden's great actresses.

It was meant to help transport wounded soldiers to a secret underground hospital.

A steel paper plane is all that remains of a crashed aircraft that caused an amazingly small amount of damage.

The remains of Alfred Nobel's first nitroglycerine factory can still be found on the shores of a Swedish bay.

This giant subway sculpture celebrates the fruit that inspired the theory of gravity.

This luxury hotel suite is located deep in the bowels of an old mine.

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

What looks like a birch tree smushed between two pieces of glass often confounds commuters.

Finally reunited, the three effigies now stand in a museum courtyard.

A wooden street sign is the last remnant of this 400-year-old alleyway.

A plaque marks the house in Stockholm where the French philosopher René Descartes lived up until his death.

A king's bloodstained shirt is among the gruesome collection of artifacts displayed below Stockholm's Royal Palace.

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

A catapult rock from Gotland’s 13th-century civil war is still lodged in Scandinavia's best-preserved medieval city wall.

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