On the far side of Uchumachi mountain the landscape changes abruptly — cloudforest gives way to vast coca plantations. A massive landslide once blocked a valley here, forming a small lake known as the Green Lagoon. It does not look like much from a distance, but it is the best swimming spot in the area. Unlike the rivers, the water is warm and the lake is big enough for a proper swim. The lakeside beach is a fine place to dry off in the sun.
Take the road that circumvents the Uchumachi from Arapata. You can arrange transport or walk.