Early prototype for Frank Lloyd Wright's Guggenheim.

Legend says train robbers stashed their gold within the depths of this unusual cave.

This massive stained-glass masterpiece is thought to be the largest Tiffany dome in existence.

A lush green oasis in the middle of Chicago.

A shining sculpture made of 3,115 lights, the number of visible stars in the Northern Hemisphere.

The only structure left with direct ties to the Salem witchcraft trials of 1692.

A collection of haunted artifacts chronicles the career of the world's most famous paranormal investigators.

It was founded by Ralph Nader to educate the public about an often-maligned area of law.

Who knew the Devil's domain was a hot spot for tubing?

Mansion and shopping center used in the 1975 film "The Stepford Wives."

Ruins of a historic medical facility sits eerily by the water.

A vast collection of rare books, manuscripts & extraordinary objects illustrating the history of medicine.

The ruins of an abandoned 18th-century town that is slowly being reclaimed by the forest.

An ADA-accessible trail and deck offering stunning views of Colorado’s Mount of the Holy Cross.

The site of a defunct mill, that once supplied marble for the construction of the Lincoln Memorial.

This old train trestle and collapsed tunnel once allowed the railroad to negotiate the steep slopes of the Colorado Rockies.

A coal fire has been burning underground here since 1896.

The site of the "Bone Wars" between two rival paleontologists during the dinosaur rush of the 19th century.

This interpretive path lets you get up close and personal with dinosaur bones.

Climb to the top of this spiritual tower, and you'll be rewarded with spectacular views.

These decaying bridges 1,000 feet high are a reminder of the skill it took to cross the Colorado Rockies by rail.

A recreation of an Old West apothecary full of curios.

This super steep hike ascends 2,000 feet in less than a mile.

This spectacular track has run continuously since 1882.