Rice Terraces, Ifugao, circa 1150 AD. The terraces cover some 3,160 acres and were built even before rice was introduced into the mountains. If the terrace walls were placed end to end, they would go halfway around the world, being eight times longer than the Great Wall of China. Contrary to common belief, the terraces are not carved on the mountainsides but are built. The pond field terrace has visible parts: the flat flooded enclosure, rimmed on the outer edge by a low retaining dike; this is surrounded by an artificial or natural slope below the dike on the downhill side, and by slopes rising from the inner flooded area on the uphill side. The terraced fields are worked entirely by hand, since there are no draft animals used. Seedlings are raised in special sections of a field then transplanted entirely by hand. Harvests are community affairs using labor exchange. The pond field also serves as a fishpond, when filled with water. During off-season, the pond soil and the straw from the field are raked into mounds and mulched. Vegetables are planted on top of these mounds.