Ancient Observatories
Casa Rinconada, Chaco Canyon

There are kivas and then there are great kivas. Casa Rinconada is one of five great kivas in Chaco Canyon. Unlike the vast majority of kivas, Casa Rinconada is not embedded in a large building complex, but stands on top of a small hill a good distance away from large buildings. It also stands partly above ground, unlike most kivas in which the roof is at ground level. Casa Rinconada is a little over 20 meters in diameter and 4 to 5 meters deep, making it one of the largest known great kivas.

While many building alignments discussed above are noteworthy, the geometrical care put into planning and building Casa Rinconada goes beyond anything else encountered in Chaco Canyon. The symmetry axis defined by the two T-shaped doors is aligned with the North-South line to within 20'. The small niches lining the interior wall are equally spaced and positioned so that lines defined by opposing pairs of niches all have their center within 10 cm of the kiva center, which also indicates that the kiva walls depart very little from a perfect circle. The circular masonry foundation sockets for the four roof posts on the kiva floor,  form a square also centered on the kiva center within 10 cm, with sides oriented to within 30' of either the N-S or E-W directions. Casa Rinconada is thought to have been designed as a physical representation of the Anasazi cosmos, and was likely used for important religious ceremony involving the larger Chacoan community.

Casa Rinconada has also attracted ---and continues to attract--- attention due to a possible solstitial alignment. Shortly after sunrise on the summer solstice, as the Sun rises a beam of light shines through a lone window on the N-NE side of the kiva and moves downward and northward until it illuminates, on the interior West wall, one of the five larger, irregularly spaced niches in the kiva. This was hypothesized to be an intentional construct, aimed at marking and celebrating the summer solstice (possibly involving the placement of offerings in the niche). There are some difficulties with this interpretation, however. The upper portions of the kiva wall were reconstructed after excavation, and it is not clear if the window was reconstructed in its original location and shape. Furthermore, the NW roof post is positioned such that it would have blocked the light beam and shadowed the niche. Finally, at some time a small room was built along the outer wall, more or less where the window now exists. All this makes it rather unlikely that the now popular solstitial "light show" was purposefully built into Casa Rinconada.

by: Courtesy of NASA

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Source: http://sunearthday.nasa.gov/2005/locations/chaco.htm

Photos: Troy Cline, Paul Logsdon

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