More than five miles of underground passageways.

Natural cathedral designed by Italian artist Giuliano Mauri.

Come for the flowers, stay for the bats!

Granite outcropping that the state's tourism bureau doesn't promote because of its delicate ecosystem.

A vertically floating hemlock controls the waves and weather at Crater Lake.

Upside-down trees serve as natural flower pots in this hanging garden of Alaska.

The stoutest tree in the world.

The fossilized remains of ancient California redwoods.

Unicorns, elephants, and bears, oh my!

A chain of 16 wondrous lakes formed as a result of the gradual dissolution of soluble layers of bedrock.

A Swedenborgian glass church surrounded by redwoods sits perched atop a massive landslide area.

America's smallest "national forest" has only 33 trees.

An underground mansion with fruit-bearing trees and grapes growing beneath the surface of central California.

Living trees form the structure of an open-air palace.

Two small chapels housed inside an ancient tree.

The sign at the garden gate reads: "These Plants Can Kill."

Home to the "Circus" trees created by Axel Erlandson.

Centuries-old bridges grown from tangled roots.

Carnivorous plants, medieval aphrodisiacs, and the largest original wood structure glass conservatory in the western hemisphere.

Home to the Amorphophallus titanum "Corpse Flower," which is among the largest flowers in the world and also smells powerfully of rotting flesh when in bloom.

The world of the ancient Celtic civilization explained through a bewitching 11 acre garden.

A cherry tree growing atop a mulberry tree.

A white oak with property rights.

A beautiful maze marks where three countries meet.