A 140-year-old castle with underground caves hidden in San Francisco.

Dramatic river bend surrounds a natural red-rocked pedestal.

An emerald-green grotto just a short trip from Austin.

This jaw-dropping 19th-century bridge uses its reflection to form what appears to be a perfect circle.

On Japan's Tashirojima Island, cats are king.

The mysterious, fantastical woodland inspiration for "The Lord of the Rings."

A tiny museum housed in a New York freight elevator specializes in the "overlooked, dismissed, or ignored."

An exquisite tunnel of cascading flowers.

Most-visited and most-photographed slot canyon in the American Southwest.

On the Oregon coast there is a natural hole that seems to be draining the sea.

One of the few remaining casualties of the London Blitz, this destroyed church has become an enchanting public garden.

A peculiar mansion built by the troubled heir to the Winchester Rifle Company fortune.

Rippling sand dunes frozen in the Arizona rock.

This astonishingly geometric cave has inspired everyone from Jules Verne to Pink Floyd.

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

A terrific purveyor of natural history objects and curios.

A huge musical instrument played by the ocean.

Pay your respects to a folk-punk legend.