Colombia's dramatic topography includes three parallel Andean cordilleras (Western, Central and Eastern) with peaks over 5,000m, separated by deep valleys like the Cauca and Magdalena River basins. The Amazon rainforest covers nearly 40% of southern territory, while the northern Caribbean coast features sandy beaches, mangrove swamps and the Sierra Nevada de Santa Marta (the world's highest coastal mountain range). The eastern Llanos are vast tropical grasslands, and the Pacific coast receives some of the world's heaviest rainfall, creating dense jungles. Unique ecosystems include the paramo high-altitude wetlands and the underground river in Caño Cristales.