A series of modernist treehouse hotel rooms grace the outskirts of an Arctic forest.

Bring your hiking shoes, wool socks, and thermal underwear for a stay in these cozy forest huts.

A rare surviving Victorian greenhouse designed specifically to house giant water lilies.

No telescopes, no power, no gift shop: The Observatory of Chichen Itza, one of the world's oldest observatories, takes astronomy back to basics.

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

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

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

A sprawling network of century-old subterranean catacombs lies beneath a nondescript suburban home.

A flooded Mexican cave that hides a river beneath the water.

An ancient system of freshwater caves filled with animal bones, including that of species long-extinct.

Few of the many visitors to this resort town know of its hidden Maya ruins.

A walk-in working camera obscura produces 360-degree live images of the San Francisco coast.

A storybook European village in Berkeley.

A hidden world of exotic succulents and cacti.

A garden oasis filled with flowers mentioned in the works of William Shakespeare.

This one-block alleyway is stuffed with street art that is colorful, cultural, and intensely political.

A speck of nature and art in one of San Francisco’s most notorious neighborhoods.

Spiral labyrinth hidden in the hills above Oakland, CA.

Bonsai garden in Oakland is curated by the first non-Japanese female bonsai master in the United States.

Julia Morgan's Moorish-Gothic labyrinth of fountains, trees, natural light and Oakland's notable dead.

Big gun installations, built over a massive cemetery, now abandoned & hidden in trees.

The last remaining relic of San Francisco's glittering 1915 Panama Pacific Exposition.

Olfactory delights in San Francisco's Botanical Gardens.

A psychedelic labyrinth on the San Francisco bay.