Pueblo Indians occupied the Frijole Creek valley up to 1550 AD, and then migrated to the Cochiti and San Ildefonso Pueblos. The probable cause of migration was extended drought. In this valley is Tyuonyi, a large circular pueblo ruin with a kiva. The walls had no doors, since entry to the rooms was through the roof.
One or two propped boulders might be a coincidence, but the ones in the above photo seem to be deliberately propped and facing southeast. There are other stone structures along the trails.
This is the famous Alcove House site, previously known as Ceremonial Cave. It contains a reconstructed kiva, and the caveates and log holes from old dwellings. Access is a 140-foot climb up four long ladders, definitely not for those afraid of heights.
On the way back, I spotted this bent tree about 300 feet from Alcove House. The bend points towards Alcove House. 500 feet further is this slope with rocks and a possible cairn. These rocks are all about the same size and shape.