The ''costa'' (coast), to the west, is a narrow, largely arid plain except for valleys created by seasonal rivers. The ''sierra'' (highlands) is the region of the Andes; it includes the ''Altiplano'' plateau as well as the highest peak of the country, the  Huascarán. The third region is the ''selva'' (jungle), a wide expanse of flat terrain covered by the Amazon rainforest that extends east. Almost 60 percent of the country's area is located within this region. The country has fifty-four hydrographic basins, fifty-two of which are small coastal basins that discharge their waters into the Pacific Ocean. The final two are the endorheic basin of Lake Titicaca, and the Amazon basin, which empties into the Atlantic Ocean. Both are delimited by the Andes mountain range. The Amazon basin is particularly noteworthy as it is the source of the Amazon River, which at 6872 km, is the longest river in the world, and covers 75% of Peruvian territory. Peru contains 4% of the planet's freshwater.