In Search of Solstices

Casa Rinconada, built between 1070 and 1110 AD, sits on an isolated hill about one-half mile across the canyon from Pueblo Bonito. One of the six great community kivas in the area, the structure is about 20 meters across and four to five meters deep. A 1970s survey of the area found this site to have precise solstice and equinox alignments. The main axis of the kiva is aligned through doorways on both the north and south sides. Modeled on a perfect circle, niches in the interior form an east-west line. Scientists who measured the alignments of these features found the accuracy of the north-south alignment to be within 45 arc-seconds or three-quarter of a degree while the error in the east-west alignment is only eight arc-seconds. Solar alignments occur on the winter and summer solstices when sunlight entering the kiva falls upon one of six irregular niches. From a given niche, the sun framed in the narrow window could be seen.