An ancient and majestic fortress that played an integral role in Portugal's road to independence.

This unreal Portuguese palace looks as though it's made from a pile of different castles.

This small chapel is built of human bones and decorated with a golden skeleton.

Perhaps the most spectacular grotto along the Algarve coastline.

Have a seat with the father of modern computing at this Manchester monument.

One of the world's largest collections of pharmaceutical artifacts.

This work of engineering is imbued with elegance and ingeniousness.

If James Bond bungee-jumped off the side of a 720-foot dam, would you do it too?

This medieval footbridge in the Swiss Alps is known to attract cliff-jumping daredevils.

The world's longest and deepest train tunnel.

This historic covered bridge contains a series of macabre paintings that communicate one thing: everyone dies.

This memorial commemorating fallen Swiss Guards of the French Revolution has been called the saddest stone in the world.

The alpine falls where Sherlock Holmes apparently met his demise can actually be visited.

A once-thriving hotel in the Swiss Alps couldn't compete with climate change.

A breathtaking bridge that crosses a vast gorge over a river's torrents, and has a tale of a devil architect attached.

The second-highest train station in Europe.

A historic observatory precariously perched at the "Top of Europe."

A cablecar-station-turned-revolving restaurant with 360-degree views of the Swiss skyline.

Caves famous for the dragon-slaying saint who lived there.

Traversing steep Alpine slopes, this engineering marvel is one of the longest and highest funiculars in the world.

The World Wide Web was created in this nondescript corridor at CERN.

An opulent monument built for a duke who donated his entire fortune to the city of Geneva.

The world's largest second-hand graces a clock surrounded by constantly changing flower beds. 

This statue pays tribute to the iconic musician in the place where he recorded his final studio album.