This scenic spot 10km south of Tupiza is the site of a narrow tunnel carved into the mountain, known as the angosto (narrow). Until 2011, the tunnel was the only thoroughfare for traffic coming to and from Villazón at the border with Argentina. The tunnel is near the juncture of the rivers Tupiza and San Juan. Where the two meet there are some striking rock formations, including la torre (the tower). The area makes for a pleasant hike.