A playground inspired by differential calculus dangles from the ceiling of the Liberty Science Center.

The spot in the Mile-High City that's exactly 5,280 feet above sea level (at least for now).

A crumbling mountain resort that looks like it was abandoned in an instant.

This morbid, delightful curiosity shop offers everything from animal bones to human teeth.

Amid the bustle and noise of the Financial District hides a secluded garden oasis above the city streets.

This massive home was constructed by one of the greatest conservationists in Colorado history.

A unique arch graces the Dolores River Canyon near the Hanging Flume.

The decaying ruins of a failed mining company’s water diversion project cling to the side of a desert canyon.

This once-popular otherworldly landscape was formed by one of the largest volcanic eruptions in history.

The site where a nuclear bomb was lowered over 8,000 feet underground and detonated as an experiment in natural gas extraction.

Unlike most arches, this geological oddity formed in a volcanic dike.

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

The remains of the dam that unleashed a 15-foot wall of water on Denver.

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

In the middle of a suburban Denver neighborhood is a cave that once provided solace for a prominent Ute chief and his family.

This iconic science fiction house still looks like something from the future.

The wreckage of a World War II bomber is hidden high in the Colorado wilderness.

The haunted reputation of these abandoned Colorado train tunnels is probably not helped by the terrifying spiked fence.

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

The world's largest carnivore sanctuary is home to over 450 meat-eating rescues.

Silver in the hills led to the speedy creation of this boom town and a lack of it saw the town abandoned nearly as quickly.

These faux-cliff dwellings allow visitors to climb around on a replica archaeological site.

Abandoned silver mine strewn with wrecked and twisted structures.

An architect in Aspen used psychedelics as his muse while building this mushroom masterpiece.