The U.K.'s first underground railway line is now a lively thoroughfare for runners and cyclists.

A true Valhalla for cactus and succulent lovers.

The fences outside some of South London's estates are made from recycled World War II stretchers.

Where condemned pirates met their grisly end at the gallows on the River Thames.

Amidst towering office buildings, a local pub lives inside Sheffield’s oldest surviving domestic building.

A striking memorial to the Jews of Leiden who were murdered during World War II is scattered throughout the city.

This Gothic castle-like portal is a testament to the amazing craftsmanship of the navvies who built the railway tunnel.

From afar it looks like someone's hat blew into the water, but closer inspection reveals a giant floating sculpture.

A 15th-century former coaching inn forms the implausibly grand entrance to a 1980s shopping mall.

This towering church is home to a world-famous organ and a treasure trove of medieval art.

The Art Deco artwork depicts gilded carriers of deadly illnesses.

Climb this overlooked gem's spiral staircase and you'll be rewarded with spectacular views of Glasgow.

Where the White Nile River dramatically cascades between Lake Kyoga and Lake Albert in Uganda.

A verdant 17th-century-style garden hidden along Edinburgh’s Royal Mile.

This quaint funicular has been ferrying people up and down an English valley since the Victorian era.

A labyrinthine network of chambers with a storied past hides below Edinburgh's South Bridge.

Watch the local Netherlands birds from inside this giant eco-egg.

The colorful stairs are made with marble from the world's major quarries.

This unique medieval court deals solely with the lead mining laws in two small areas of Derbyshire.

This 16th-century close preserves an unusual piece of Edinburgh's transportation history.

A beautiful medieval bridge allegedly constructed by the Devil.

This peculiar Italian elevator runs both horizontally and vertically.

This cliff-face port is considered a masterpiece of mining engineering.

The elegant manor house where Kaiser Wilhelm II lived in exile after World War I.