Pigduck of Turku.

A vast array of tropical plants collected by a vacationing couple.

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

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

A statue honors the children who fought Nazis in Poland.

A tribute to the Polish insurgents who fought in the failed attempt to end their city's Nazi occupation.

The former Nazi concentration camp stands as a museum to remember this dark chapter in European history.

An underground city of salt.

The picturesque birthplace of Icelandic democracy is drenched in the blood of its brutal past.

The oldest hall in Iceland was written of in the Sagas and features a centuries-old escape tunnel.

A formerly glacier-tipped volcano that inspired none other than Jules Verne.

A sulfuric martian landscape that looks far better than it smells.

If a glacial river suddenly diving into a sheer chasm via a dramatic, multi-stage waterfall isn't peak Iceland, it's certainly close.

This valley of hot springs and boiling mud pots is home to the record-holding "Geysir," which originated the English word.

This eye-popping Icelandic crater lake is surrounded by red volcanic rock.

One of the tallest buildings in Iceland, and perhaps, the most visually impressive.

Iceland's largest lagoon is home to stunning multi-colored icebergs.

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

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

Gaudí's famously flamboyant architectural style is on full display in this sprawling park and garden.

One of Antoni Gaudí's most classic buildings is well-known for its "dragon-back" design.

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.

This insurance company building reminds customers that witches, bears, and gnomes are out there, best be insured.

An abstract monument to a symphonic composer.