Mayan civilization lasted for more than 2,000 years, but the period from about 300 A.D. to 900 A.D., known as the Classic Period, was its heyday. During that time, the Maya developed a complex understanding of astronomy. They also figured out how to grow corn, beans, squash and cassava in sometimes-inhospitable places; how to build elaborate cities without modern machinery; how to communicate with one another using one of the world’s first written languages; and how to measure time using two complicated calendar systems.