A narrow strip of land is home to the tallest migrating dunes in Europe.

This large copper bolt represents the benchmark for measuring sea levels in most of Europe.

Amsterdam's narrowest house facade is a monument to 17th-century tax evasion.

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

This hunter-gatherer architecture is believed to be the oldest religious complex known.

Roman ruins top white travertine terraces formed by ancient hot springs.

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

This massive Trojan ursine was built to be a new tourist symbol for a small Swedish town.

Budapest's Communist-era statues, banished to the suburbs.

Possibly the world's largest hourglass only needs to be reset every New Year's Eve.

A trail of iron footwear stands as a monument to the thousands executed along this riverbank during WWII.

This tree was once used to calculate the decrease of the Baltic Sea.

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

An otherworldly, fossil-rich cobble beach holds Viking graves, cairns, and other remains.

Archaeologists are still unraveling the secrets of the brutal massacre that wiped out this ancient fort.

A forest of immensely tall and unusually straight oak trees planted nearly 200 years ago to build naval ships that never came to be.

Sound travels strangely in this underground whispering gallery.

The single richest source of elemental discoveries in the world.

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

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

Built in 1870 at the bridge that connected Buda and Pest, this spectacular incline railway was almost lost forever during World War II.

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

Mysterious craters may have been home to an ancient cult.

Giant, friendly pelicans in Central London, the most unlikely of places.