The Mayans had a great empire in Central America over 1500 years ago. They built breathtaking pyramid temples and structures out of limestone. Their architecture and advanced calendars that could predict astronomical events were remarkable technological feats for their time. The Mayans had an intricate religious system that involved human sacrifice to gods representing nature and war. They also developed a complex numeric system and one of the earliest forms of writing in the Americas dating back to 250 BC.