The Aztecs had many gods that represented natural elements and human activities. They built intricate systems of raised gardens called chinampas in lakes to grow multiple crops annually. The Aztec Empire expanded through both trade and military conquest between 1427-1521, ruling over Mesoamerica. Human sacrifice was an important religious practice, with war captives' hearts often ripped out and offered to the sun god Huitzilopochtli. The Aztec calendar consisted of a 260-day ritual cycle paired with a 365-day year count cycle. Their capital of Tenochtitlan was built on islets in Lake Texcoco in a symmetrical layout with canals for transportation and the Great Pyramid at its center