The Quebrada de los Cuervos is a gorge sunk a hundred metres without warning into the open grassland of the Treinta y Tres department, in eastern Uruguay, its sheltered floor holding a subtropical forest at its southern limit, with vultures nesting on its cliffs, and it is walked down into from the sierra on a path that drops from the pampas into another climate in half an hour. The gorge was cut by the Yerbal Chico stream through the hills of the Sierras del Yerbal, and the stone is not one stone, since granite a billion years old lies against sandstone far younger; the sheltered floor traps warmth and moisture, so palms, ferns and the trees of the Brazilian forests grow at their farthest south, and the path down loses the full hundred metres with the palms that were crowns seen from above arriving at eye level, then overhead, to the stream and the pools at the bottom. The cuervos of the name are vultures, three species of them, and nothing rises until the rock has warmed, so they sit on the cliff ledges early and are in the air from late morning, riding the thermals past the rim where the walkers watch them at eye level.
The grassland above the gorge is most of what the protected area covers, 19,395 hectares of which much is private land where families still graze cattle, and from mid-November it fills with the capuchino seedeaters, small threatened finches that fly down from the north to breed and are gone by March, the reason the range is an Important Bird Area. The name of the sierra comes from the wild yerba mate that grows in the gorges, since Uruguay drinks more mate per person than any country and grows almost none of it. The park is the first protected landscape of the country, with a campsite on the rim and a ranger station. The Quebrada de los Cuervos is a slice of the tropics hidden in the pampas, and the vultures are its keepers.