a prehistoric observatory...

"notice the small circular window in the upper left potion of the west wall. the opening aligns with the setting sun on the summer solstice (jume 21), the longest day of the year. the square hole in the upper right wall aligns once every 18 ½ years with the setting moon at an extreme point in its cycle. other windows and doorways in the upper part of the building also align with the sun or moon at significant times of the year.

it appears that the hohokam devised a calendar system based on the motions of the sun and the moon, and incorporated that knowledge into their architecture. like england's stonehenge, the casa grande may have served as an astronomical observatory and calendar."

images of casa grande, the big house, visited en route to marfa, traversing arizona. the ruins sounded interesting because of the mud skin on the architecture, but i was surprised to find the relationship to the moon and sun cycles. the quotes are from some signs posted by the national park service. the structure and history were quite amazing. it was built sometime between 1300 and 1400...