Legend has it that a hero called Tacaynamo landed his fleet of balsa rafts on the shore of Peru in the year 900 CE and founded the Chimú city of Chan Chan. Over the centuries, the population of Chan Chan grew to 50 000 inhabitants, as many as half of whom were artisans. The artisans worked in royal compounds surrounded by high adobe walls to control sand and dust. The city walls also acted as passive solar collectors to insulate against desert heat in the daytime and release the heat at night as the temperature fell. The buildings of Chan Chan were decorated with mosaics of adobe bricks and bas-reliefs of stylized animals, birds, and mythological creatures. Dwellings were open to the sky, since it seldom rains on the desert coast of Peru. Farms were irrigated by a system of canals fed by streams falling from the western face of the Andes mountain chain. Garden plots, sunk to the level of the water table and fertilized with guano mined from bird islands, grew beans, corn, pumpkins, sweet potatoes, yucca, peppers, peanuts, plums, papaya, cotton, and avocados.