Of all the world’s ancient calendar systems, the Maya and other Mesoamerican systems are the most complicated and accurate Maya astronomer-priests looked to the heavens for guidance. They used observatories, devices to cast shadows, and watched the horizon to trace the movement of the sun, stars and planets.

They calculated and recorded the information in books known as "codices". The Maya developed calendars to keep track of celestial movements and the passage of time.

In Maya cities, ceremonial buildings were precisely built according to compass directions. At the spring and fall equinoxes, for example, the Sun casts its rays through small openings in a Maya observatory

The most famous example of this kind of alignment is at Chichén Itzá, the best known Maya city of the Yucatán Peninsula.

It is a short airplane ride from Cozumel, world-famous for scuba diving, and a day trip from the beaches Cancun, one of the top vacation destinations in the world. The sun lights the stairs of a pyramid dedicated to Quetzalcoatl, the Feathered Serpent god. At the vernal and autumnal equinoxes (April 21 and September 21), the Sun gradually illuminates the pyramid stairs and the serpent head at its base, and looks like a snake slithering down the sacred mountain to Earth.

The "Caracol" at Chichén Itzá is thought to be an observatory. Some of its doors and windows line up with orbits of some planets. At Palenque, Pacal’s tomb in the Temple of the Inscriptions is lined up with the path of the Sun. At winter solstice, the Sun sets behind a ridge beyond the temple, in line with the center of the temple roof. As the Sun crosses the sky, it enters a doorway and appears to light the stairway into Pacal’s tomb.

This symbolizes his death and entry into the Underworld. Another temple at Uxmal contains hundreds of Venus symbols. The Dresden Codex, one of four surviving Maya chronicles, contains much information on the cycles of the planet Venus. War related to the movements of Venus was common.

The Maya believed that the gods guided the Sun and Moon across the sky. Even in the darkness of night, the Maya believed that the Sun and Moon continued to journey through the Underworld. All the way, they were threatened by evil gods The Maya believed that the sun and Moon needed help from humans.