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

The marker offers a rare chance to be in four U.S. states at once, though there's some controversy over its geographic accuracy.

This Old West prison built into the side of a cliff was said to be inescapable.

Hike the unusual hoodoos and rock formations that form this little-known natural wonder.

Some of the tallest ancient American ruins continue to inspire awe and curiosity.

The world's largest rose bush has literally outgrown the pioneer museum it was planted behind.

The Jewish section of the famous Boothill Graveyard was abandoned for nearly 100 years.

Limestone caves with spectacular showcase chambers.

A reproduction of earth's many biomes.

After a short-lived attempt to bring America in line with the rest of the world, this road was left in metric.

This iconic 1958 tower welcomes air travelers to Tucson with neon-lit letters and architectural style.

A technicolor place of worship for Elevationists.

An off-the-beaten path cave with an underground lake.

The fading, forgotten remains of a once bright and booming factory.

The man who wasn't there.

The world's second-longest burning light bulb.

A modernist landscape of water and sci-fi concrete.

See the sky in a new way through this art installation.

The final resting place of infamous outlaw Clyde and Marvin Barrow.

The final resting place of an outlaw, whose legend grew after death.

A "Texanic" (gigantic Texas) collection of Art Deco architecture at Dallas' historic Fair Park.

This collection of bronze hands comes from astronauts, presidents, baseball greats, and more.

A trio of colossal statues spread across a Dallas neighborhood chart the emergence of a giant robot born of a locomotive and spilled gin.

This downtown Dallas art installation is always on the lookout.