This colorful creation wasn't always a welcome part of Toronto's Moccasin Trail Park.

In Hong Kong, a fairytale flower tunnel is hidden within the gardens of a public housing complex.

The romantic botanic tunnel feels like a well-kept secret.

A repurposed railway tunnel with otherworldly acoustic characteristics.

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

This former train tunnel is filled with lines from a poem crafted by Robert Louis Stevenson.

This brick-lined pedestrian walkway was once a railway tunnel used during the Civil War.

Home to the longest wooden escalators in the world.

Once a sewer culvert, this road tunnel now offers cyclists and pedestrians a subterranean stroll under the C&O Canal.

An abandoned railroad tunnel transformed into a creepy path for hikers and cyclists.

This nondescript tunnel has been featured in a number of iconic movies, from “Roger Rabbit” to “Back to the Future.”

Greenery cloaks this serene sculpture inspired by the famous Lost Gardens of Heligan.

This massive redwood tree has stood in Northern California for nearly 2,000 years.

Home to an endangered salamander, a full moon celebration, and a large spring-fed outdoor swimming pool.

A natural tidal swimming pool is ringed by bizarrely artistic lava rock formations.

At the foot of a waterfall lies a peaceful swimming lagoon and evidence of over 60,000 years of human habitation.

These azure waters were thought to lead to the Mayan Underworld.

A clear blue swimming hole with hidden caves, still unexplored.

The world is full of swimming holes, but few compare to Samoa’s idyllic To Sua ocean trench.

There's a mini version of Iguazu Falls hidden in the Balkans, and it's got a rope swing.

Take a dip beneath the stalactites in this amazing cenote.

This geothermal hot spring hides beneath a slowly growing mineral dome.

A perfectly circular lake is formed by the crater of an ancient underwater volcano.

The gathering point of an old Melbourne swimming club was site of a historic, world-record dive in 1918.