It is not known how many people lived in Venezuela before the Spanish conquest; it has been estimated at around one million. In addition to indigenous peoples known today, the population included historical groups such as the Kalina (Caribs), Auaké, Caquetio, Mariche, and Timoto–Cuicas. The Timoto–Cuica culture was the most complex society in Pre-Columbian Venezuela, with pre-planned permanent villages, surrounded by irrigated, terraced fields. They also stored water in tanks. Their houses were made primarily of stone and wood with thatched roofs. They were peaceful, for the most part, and depended on growing crops. Regional crops included potatoes and ullucos. They left behind works of art, particularly anthropomorphic ceramics, but no major monuments. They spun vegetable fibers to weave into textiles and mats for housing. They are credited with having invented the arepa, a staple in Venezuelan cuisine.