Argentina has 4725km of Atlantic coastline, which comprises three main types of habitat. From the mouth of the estuary of the Río de la Plata to just beyond the southern limit of Buenos Aires Province, the shoreline is mainly flat, fringed by dunes, sandy beaches and pampa grass. South of Viedma begin the endless stretches of dessicated Patagonian cliffs ( barrancas ) such as those you see fronting Península Valdés, broken in places by gulfs and muddy or shingle river estuaries, but almost entirely devoid of vegetation. The most beautiful of these cliffs are the porphyry-coloured sandstone ones near Puerto Deseado. The third section of coastline is that found south of Tierra del Fuego's Río Grande, where you find, in succession, patches of woodland, the bleak moorland tundra of the Península Mitre, and the rich southern beech forests of the Beagle Channel, exemplified by those in the Parque Nacional Tierra del Fuego