Take a drunken tour inside the world's largest known geode.

A winding path built in secret on the edge of the continent.

One man's prolific, decade-long quest to turn trash into artistic treasure.

A playground built by the kids that is a child's wonderland, and a helicopter parent's nightmare.

Handmade treasures from around the world.

Travelers exchange letters with woodland creatures at this mini post office.

A working model of the entire San Francisco Bay and much of the Sacramento River Delta, complete with regular tides that change every 14 minutes.

A hidden subterranean installation offers a view of the sky.

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

Get lost in this haunting fairytale art walk through a man-made eucalyptus grove.

An immersive environment that is part haunted house, part choose-your-own-adventure, and part jungle gym.

America's most famous piece of self-built architecture.

An abandoned facility that has become a place of ritualistic satanic worship, or so rumor has it.

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

The only theatre in the world constructed specifically for sound movement.

A hand-built folk art installation covered with messages of God's love.

One man has carved a number of natural New Mexico caves into psychedelic sandstone temples.

The ghostly remains of an accidental sea.