Maya civilization begins and flourishes for centuries in present day southern Mexico and Central America. Especially from 250 to 900 CE, the Mayan people formed a highly advanced civilization which included developments in art, mathematics, calendrics, and architecture (including flat-topped pyramids, temples, and towers that are still in existence today). The Mayans were probably the first people in the western hemisphere to develop a writing system. Their 365-day calendar is considered by many experts to be even more precise than the 365-day Gregorian calendar in use today.