The Cesar Chavez Memorial Solar Calendars in Berkeley, California, were inspired by design concepts in art, astronomy, ecology and architecture at varied sites of ancient sky observatories around the world. The Cesar Chavez Memorial Solar Calendars, designed and built by Santiago Casal, include a Horizon Calendar using an interplay of the Sun and Earth by tracking the position of the sun along the horizon over the course of year. A visitor stands in the center of the horizon calendar circle, aligning the small inner stones with the larger boulders around the perimeter of the circle – oriented to sunset and sunrise points on the western and eastern horizons (marking the start of the seasons). The Meridian Calendar (with the gnomon) casts a shadow to measure the altitude of the Sun on the meridian at solar noon. The triangular pointed tip of the gnomon (obelisk) casts a shadow on the tile base.