This trail was once used to smuggle cigarettes, sugar, and other black market goods between Italy and Switzerland.

The Sighignola summit on the Swiss border offers views so breathtaking it's been named one of the most beautiful places in Italy.

A former ironworks that was the first UNESCO industrial site.

A suspended footbridge allows for traversing this gorge carved through the French Alps.

Each spring, a dreamlike carpet of bluebells overtakes the forest floor.

Take a leisurely walk through the park to find the seven giant troll sculptures hidden throughout the park.

The largest 19th century panorama in the world still in-situ.

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

A long spiraling walkway winds through the woods, and around a copper beech tree at the center.

Denmark’s never-ending bridge.

A 19th-century subterranean reservoir repurposed as a contemporary art cave.

This Dutch windmill has its roots in an American invention.

At the base of this tower, a plaque marks the original center point of the Netherlands.

Nestled in the woods lies this land art project: a hybrid between park, maze and natural monument.

Repurposed space and ultra-modern construction collide to create this geometric wooden spectacle.

An enormous concrete structure built over a nuclear crater.

This World War II airfield enjoys a second life as a public park.

Gutted airplanes slowly decay in a Florida field.

A community of collapsing homes more than a mile out from the Florida coast.

This artificial ring island was built to hold cubic tons of polluted dirt.

This steel frame is a skeletal mirage of a lost 16th-century stone building.

This large sand dune in the Netherlands is home to wind-whipped trees with "floating" roots.

Lombardy poplars planted to imitate the size and shape of the Cathedral of Notre-Dame de Reims.

A set of 27 bamboo tubes creates an eerie soundscape that changes with the wind.