This unusual rock looks like a giant, otherworldly mushroom sprouting atop a cave.

According to legend, this boat-shaped henge is built over the grave of a mythic king.

The second oldest anatomical theater is housed in a museum of curiosities.

Crooked windswept pines give this old forest an enchanted and magical look.

This encrypted monolith protected a secret of Norse mythology by hiding in a church wall for over a millennium.

Stockholm's deepest subway station is also a stunning ecological wonder.

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

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

A hidden bathhouse in one of Stockholm's oldest and busiest neighborhoods is open to anyone who can find it.

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

A series of modernist treehouse hotel rooms grace the outskirts of an Arctic forest.

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

A rare octagonal brick beacon on an isolated island in the Baltic.

A cathedral resurrected from the ashes of one of Europe's greatest urban fires.

The church's remarkable frescoes incorporate Finnish artist Hugh Simberg's trademark themes of death and the supernatural.

The etchings on this narrow channel between two islands bear witness to maritime travelers who have passed through since the Middle Ages.

This disused church, left to the elements of the Arctic Circle's forests is open for exploration.

A 246-foot-high revolving restaurant rises unexpectedly from a forested Finnish hilltop.

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

Legend has this precariously placed rock was placed by giants. Science has another explanation.

A subterranean house of worship carved right out of the bedrock.

Architecturally stunning library serves as the hub of Finnish scholarly life and culture.

Rent out a glass igloo to watch the Northern Lights like you live in the future.

This metal tower in the desert provides views of a handful of Nazca geoglyphs.