This semi-secret garden in south Seattle emulates a traditional Japanese garden using the plants of the Pacific Northwest.

A giant Troll lurks under one of Seattle's oldest bridges.

This medieval Estonian tower provides access to a series of tunnels that have been home to soldiers, punks, and fine art.

Estonia's largest creative city is a vibrant bohemian hub located within a former industrial complex.

Disused seaplane hangar gets a second life as the jaw-dropping home of Estonia's museum of maritime history.

A secluded art gallery hidden within the cellars beneath Tallinn’s medieval monastery.

"There's nothing there," and other lies the KGB told us.

Cool down and fill up after visiting Teotihuacán at this bar and restaurant in a deep, underground cave.

An underground nightclub helped spark a "Singing Revolution."

One of the few places where you can visit a cenote and Maya ruins at the same time.

This cavernous swimming spot doubles as a home to the largest known colony of bats in Central Asia.

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

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

A long-forgotten Victorian swimming hole is still a fun spot for a dip.

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.

A magical sinkhole on the Yucatán Peninsula is adorned with mini waterfalls and hanging vines.

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

Unparalleled stargazing, one of Colombia's best observatories, and a swimming pool can all be found in the middle of this ancient tropical forest.

A sinkhole and now a swimming hole, too, full of dazzling turquoise water.

This rare, carefully curated collection showcases the history of neon inside a grandiose Elks lodge.

Portland had a unique approach to Cold War-era protections.

This drowning bronze monument marks the spot where one of Australia's great engineers died by suicide.