The Pampas, also known as the Pampas Plains, are fertile low grasslands in southern South America that cover more than 1,200,000 km2 (460,000 sq mi) and include the Argentine provinces of Buenos Aires, La Pampa, Santa Fe, Entre Ríos, and Córdoba; all of Uruguay; and Brazil's southernmost state, Rio Grande do Sul. The vast plains are a natural region, interrupted only by the low Ventana and Tandil hills, near Bahía Blanca and Tandil (Argentina), with a height of 1,300 m (4,265 ft) and 500 m (1,640 ft), respectively. This ecoregion has been changed by humans, especially since the release of animals like cattle, pigs, and especially sheep onto these plains.