An unfinished tomb carved into a giant boulder in the Arabian Desert.

A rare surviving Victorian greenhouse designed specifically to house giant water lilies.

These quaint cottages feature built-in signaling devices for fishermen.

This lake’s emerald green waters are a spectacular sight, but it’s not a great place for a swim.

Enormous sandstone towers loom within a Czech forest.

The pretty iron lamp is a reminder of the architecture underneath London's streets.

This enchanting mountain plateau celebrates spooky local folklore.

A series of modernist treehouse hotel rooms grace the outskirts of an Arctic forest.

The concrete skeletons of an abandoned Swedish town hide among the trees.

This alley off Edinburgh's Royal Mile contains remnants of the city's seedier history.

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

A coal fire has been burning underground here since 1896.

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

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

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

One of the few surviving Panama Canal steam shovels stands outside a tiny Colorado mining museum.

This 19th-century ranch is being transformed into a residential library with thousands of books about the natural world.

This statue of an obscure comic strip hero stands as a tribute to patriotic service and a cautionary tale about embracing fads.

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

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

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

The giant stump of the once towering cottonwood where Ute people held tribal meetings.

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

This sidewalk tribute honors Colorado's great culinary creation.