What were the American (aka built by these tribes: Maya, Aztec, Inca, and so on) pyramids made of?

Like many Mesoamerican pyramids, each was constructed around a core of rubble held in place by retaining walls. The walls were then faced with adobe bricks, and then covered with limestone. The base of the Pyramid of the Sun measures 730 feet per side, with five stepped terraces reaching a height of some 200 feet.