Cahokia was a pre-Columbian city laid out on a celestial grid. People who lived there created solar calendars as landmarks. Archeologists found the remains of one such calendar. It stood as a ring of wooden posts. (So, the name Woodhenge).
Through observation of the position of the sun at sunrise, the people designed it such that the sun seemed to rise from one post at one time of the year and then another later in the year. One post corresponded with the winter solstice, another the equinoxes, and another the summer solstice.
With this calendar, observers could tell when to plant and harvest crops and when to gather for festivals. With tools, human ingenuity link the sky and the earth in a productive and commonplace way.
Click here to a clip about Woodhenge from the PBS special Native America.