The Observatory temple or El Caracol, as it is called in Spanish, is located at Chichen Itza's Central Temples Group. A fascinating Mayan architectural design, shaped similar to a modern Observatory structure. The central cone building features doors and windows are aligned to various astronomical events and for the observation of the stars and planets movement; Mayan astronomers had a detailed understanding of Venus, the Sun, and the Moon as they traverses the heavens.
For detailed information about the Maya Calendar System, Cycles and Facts, please read the article The Maya Calendar System, a brief introduction and facts about the amazing multiple Maya Calendar systems based on the Sun, Moon, Venus, and our Planetary system in relationship with the Cosmos.