The ranges appear to line up in accordance to equinoctial, solstitial or midsummer sunrise points. The second group contains ecliptic, solstitial, and equinoctial rings that turn as a unit. The bisector of the observatory's solstitial arc lies in line with the Acropolis. This makes the solstitial colure point towards the North Celestial Pole and Polaris. A solstitial celebration is held on Casper Mountain at Crimson Dawn park. Eratosthenes most probably used a solstitial armilla for measuring the obliquity of the ecliptic.