The Plains Indians built their houses with the only materials they had: the skins of the buffalo they hunted or the soil dug from the earth around them. Homes grew larger and more varied with the arrival of the horse. The earthlodge, dating from AD 700, was larger than the tipi of buffalo hide. Both were laid out according to religious beliefs and symbols, as were arbors, burial platforms, sweatlodges, and the impressive structure for the Sun Dance.