Mystery Photo 50 was taken in the Sun Temple, an Ancestral Puebloan ceremonial structure located on the mesa top across from Cliff Palace in Colorado’s Mesa Verde National Park. The cropped photo was taken inside the pair of widely-spaced walls forming the structure’s perimeter. Evidence suggests that these walls, which are double-coursed with a rubble core, may have been up to 14 feet tall. The modern concrete that caps the Sun Temple’s walls was put there to weatherproof the rubble inside the walls.

The D-shaped Sun Temple, which had two circular rooms -- perhaps tower-like structures? -- is one of the largest ceremonial structures that the Ancestral Puebloans ever built. It was apparently abandoned in 1276 before it was completed.

“Sun Temple” may very well be a misnomer. Scientists aren’t sure why the structure was constructed, or why it wasn’t finished. Eroded markings on a boulder that might have served as a sun dial suggest that marking the change of the seasons might have been one of its functions.

Congratulations to the Traveler readers who ID-ed the photo: Eric Nelson, s, Fewkes, ajsharon, and RangerLady. All are eligible for our monthly prize drawing.