Large military radio station without transmitting towers.

The largest cave in Northern Europe.

The last fully functional fortress of Germany's World War II Atlantikwall.

A thin pane of glass keeps visitors from sliding off this futuristic skywalk.

Stay overnight in the world's most sleekly designed rabbit hole, free of charge.

One of the most breathtaking railways in Europe also takes one of the steepest climbs, from fjord to mountain plateau.

Walk behind a 50-meter-high waterfall.

Monuments don't get much more metal than these three giant viking swords planted in a Nordic hill.

This giant boulder is pinched over a 1000-meter abyss by two mountains.

This "preacher's pulpit" once used for pagan ritual, is home to a new, and dangerous ritual.

Norway has built what may be the world's most beautiful public toilet.

A serpentine highway twists and turns over the treacherous Norwegian Sea.

Walk 2,300 feet above the ground on the "Troll's Tongue."

The internet as provided by a James Bond villain.

This Stockholm light tower can be controlled by anyone with a smartphone.

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

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

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

An alien church provides much needed silence in the midst of a Finland shopping center.

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

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

The Guardian of Tallinn.

Estonia's largest creative city is a vibrant bohemian hub located within a former industrial complex.

A secluded art gallery hidden within the cellars beneath Tallinn’s medieval monastery.