In the days before house numbers, these colorful signs held clues about various buildings' purposes.

The world's oldest Jewish library was founded by Sephardic Jews in 17th century Amsterdam.

A unique collection of gilded age mechanical pianos.

This unusual elevator doesn’t stop or slow down.

This museum housed in a former brothel explores the past and present of sex work in Amsterdam.

A beautifully eclectic mix of architectural styles.

A Dutch passageway's artistic, aquatic-themed makeover pays tribute to the capital city's famed waterways.

The world's only museum devoted to the wonders of fluorescence.

A scandalous Art Nouveau collaboration that set Paris all atwitter at the turn of the century.

Nicknamed the "Museum of Horrors," this French anatomical collection has been fascinating visitors for over a century.

A huge Megalithic chamber tomb located behind a cafe.

This unique rock formation is quite the local celebrity, although one day it may come crashing down.

An untouched lava tube accessible to the adventurers.

This local emblem is the oldest and largest dragon tree in the Canary Islands.

An unexpected ghost village lurks on the southeast coast of Tenerife.

This 22-floor tower's Skydeck offers panoramic views of Amsterdam.

The compass on its front was a handy tool for 17th-century merchants who needed to know the direction of the wind.

The old observatory in Copenhagen has a spiral corridor used as a racetrack.

Hotel designed by indie graphics artists.

A little-known cafe in an old copper bridge tower with 360-degree views of the harbor.

Visitors are treated to a stained glass kaleidoscope interior inside this work of art.

Danish tourist destination well known for open stalls where vendors sell marijuana on the street.

Climb to the top of its spiral spire for spectacular views of Copenhagen.

Opulence and fantasy collide in this royal chair which is supposedly made with unicorn horns.