El General and Coto Brus Valleys, on the southern Pacific side of the country, are watered by the River Térraba, which is the longest River in Costa Rica (160 kms.). It begins on the southern slopes of the imposing Talamanca Mountain Range. Together with the River Sierpe, and once near the sea, it forms a network of channels and islets of great scenic beauty, thick with lush foliage typical of mangrove swamps. These habitats protect a large number of birds, snakes and mammals that can easily be seen thanks to the navigable channels. The Térraba is navigable for 22 kms. upstream, as is the river Sierpe, and is frequented by small watercraft that link the little villages near the mouth of the river with the river port of Sierpe.