On this site at a high elevation in the Mexican State of Oaxaca is a plaza of ancient structures. One structure is noticeable in that it is about 45° out of line with the others. A sight line from the front stairway of it, perpendicular to the steps, and projected to the horizon meets the point where the star Capella is seen at dawn for the first time each year. This is also the day of the first zenith passage of the Sun. Thus, when they saw the star Capella at the right spot, they knew that the Sun’s zenith would appear that day.