"El Caracol" observatory temple

El Caracol ("The Snail") is located to the north of Las Monjas. It is a round building on a large square platform. It gets its name from the stone spiral staircase inside. The structure, with its unusual placement on the platform and its round shape (the others are rectangular, in keeping with Maya practice), is theorized to have been a proto-observatory with doors and windows aligned to astronomical events, specifically around the path of Venus as it traverses the heavens