Ahu evolved from the traditional Polynesian "marae". In this context, "ahu" referred to a small structure sometimes covered with a thatched roof where sacred objects, including statues, were stored. The ahu were usually adjacent to the marae or main central court where ceremonies took place, though on Easter Island, ahu and moai evolved to much greater size. There the marae is the unpaved plaza before the ahu. The biggest ahu is and holds 15 statues, some of which are high. The filling of an ahu was sourced locally (apart from broken, old moai, fragments of which have been used in the fill). Individual stones are mostly far smaller than the moai, so less work was needed to transport the raw material, but artificially leveling the terrain for the plaza and filling the ahu was laborious.