The Gran Chaco is approximately 1,500 km (932 mi) from north to south and 700 km (435 mi) from east to west, passing through the political boundaries of Argentina, Bolivia, Paraguay and a small section of Brazil. The Gran Chaco is a generally flat area that slopes slightly to the East. Rainfall increases from west to east and primarily occurs in the summer months. Vegetation is dominantly comprised of open dry woodland with cacti and bromeliad species and an understory of grass.