An artsy hidden staircase leads to breathtaking views of San Francisco.

Inside an old airplane hangar, friends and strangers alike play on a massive trampoline.

A hidden subterranean installation offers a view of the sky.

The old Niles Canyon Aqueduct in the San Francisco Bay Area is a bemusing and secret trail through nature for wayward travelers.

An vast warehouse of everyday treasures in Berkeley, CA.

340 bicycles, 65 feet high.

A popular tourist cave with a dark past.

A ruined hotel with an unlucky history and an eerie present.

The fossilized remains of ancient California redwoods.

The largest drain hole in the world.

A bike being "eaten" by a tree is the real Vashon legend behind popular children's book, "Red Ranger Came Calling."

Bridges, terraces, and replicas of historic structures all built of rock and petrified wood by one man.

The longest continuous lava tube in Oregon.

100-year-old shipwreck you can walk up to at low tide.

You might know it as the Overlook Hotel, but the inside is not going to be familiar.

Two massive rock outcroppings on the Oregon coastline.

The longest continuous lava tube in the continental U.S. offers 2.5 miles of dark explorations for the adventurous.

1920's mining camp and environmental education center is serving to protect the surrounding forest, one of the last of its kind in the Pacific Northwest.

Hollowed out cedar log tubs set in an ancient towering forest.

An extraordinary mixture of natural beauty and man-made phenomena.

This bridge provides safe passage for squirrels.

World's largest porcine hairball sits in a collection maintained by Benedictine monks.

One of the world's tallest, oldest, and most disgusting chocolate cascades.

A roaring, awe-inspiring double cascade of icy water flows through woodland Oregon like something out of a Tolkien novel.