Caption: El Caracol, Chichen Itza (constructed circa 906 CE) is a likely astronomical site of ancient Mayan astronomy. Chichen Itza is believed to have flourished in the period circa 750--1250 (see Wikipedia: Chichen Itza: History).

Features:

1. Note Chichen Itza is an ancient Mayan city in the Yucatan state of Mexico.

2. El Caracol is NOT only considered to be a likely astronomical site, but also an actual likely observatory: i.e., a building for gathering new astronomical data.

3. The tower (whose original shape was a smaller cylinder on top of a larger one) is conjectured to have allowed Mayan astronomers to view the sky well above the vegetation which blocked much of the view of the sky. In particular, the tower would have allowed Mayan astronomers to see horizon phenomena (risings and settings) better. Horizon phenomena were often considered very important in early astronomy.

4. The possibility that El Caracol was an observatory, even in a very elementary way, distinguishes it from most astronomical sites which were almost certainly just records of astronomical knowledge, as well as serving other probably much more important cultural functions, and were NOT observatories.

5. For more information on El Caracol, Chichen Itza, see Echoes of the Ancient Skies: The Astronomy of Lost Civilizations (1983), p. 52--58 by Edwin C. Krupp (1944--).