Octave, Arizona

This 266-acre property in Arizona isn't much to see from above ground: cacti, dirt and a 2-bedroom manufactured home, two hours from anywhere. The reason for the property’s $5.9 million price tag is hidden underground: 25 miles of tunnels into what was once one of the richest sources of gold in the U.S. The first people to discover the mine reported that the area was littered with gold nuggets the size of potatoes, according to a book on the Weaver Mining District.

In its heyday in the late 1800s, Octave was a bustling town with a school, a post office, a general store and a stagecoach line. The mines there were some of the most productive in the Old West before the area was abandoned by Asarco in 1940s.

The mine was featured in a short-lived cable show called “Ghost Mine,” where paranormal experts explored reports of ghosts in abandoned mines, including the spooky and notorious “Blue Devil of Octave.”