Paleoamericans built these ancient walls high in the Colorado Rockies as part of an extensive hunting system.

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

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

The site of a minor battle might have been forgotten if not for one participant’s famous family and the death of a respected warrior.

Wondrous sandstone hoodoos where Native Americans collected clay for pottery, 9,000 years ago.

This atmospheric ruins are truly a sight to behold.

Colorado's only active volcano last erupted around 4,000 years ago.

Within the former ghost town of Cisco is a carefully restored tiny town with one resident and its own art residency.

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

A coal fire has been burning underground here since 1896.

A little-known hot spring haven right below the highway.

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

Cliffs that hold fossils, including the earliest known reptile, dating back more than 300 million years.

Fossils, railroads, and waterfalls!

The ruins of the "20-year town" lay out among the mountains of Alberta.

The remains of a Canadian train crash are now mouldering beneath layers of rust and graffiti.

These strikingly barren, rolling red hills were caused by bad farming practices.

Defying all odds, this lonely little tree found a home on a log sticking out of a Canadian lake.

This expansive bridge in the Canadian wilderness was originally just built for friends.

This natural sea cave hides a small wonderland of natural turquoise beauty.

Railways may have forged this quintet of lovely tunnels, but now they are open to hikers.

A well-preserved network of cavernous tunnels have spent silent centuries removing Toronto's waste.

Designed by Buckminster Fuller, this relic of the 67 Expo survived fire and ice.

This Elizabethan hedge maze is one of only six in North America.