South of Managua , the land crumples into high cloudy ridges and the windblown peak of Las Nubes (934 meters), then falls off slowly until it spills into southwestern Nicaragua’s plains.
Here Lake Cocibolca presses the land into a narrow belt that barely separates the lake from the Pacific Ocean. In fact, geological evidence suggests at one point, it didn’t separate them at all, and Lake Cocibolca once flowed across this slim margin of land to the west, draining into the Pacific near the fishing community of Brito rather than down the Río San Juan  into the Atlantic Ocean, as it does today.
The isthmus of Rivas is replete with history. Although known as the land of Nicarao, the area was first inhabited by the Kiribisis tribe, whom the more powerful Chorotegas pushed aside. The Nicaraos came afterward, and by the time the Spanish “discovered” the region, had been residents here for at least seven generations.
Rivas , a languorous colonial town of traders and farmers, watched hundreds of thousands of passengers traveling between New York and California pass through its streets in horse-drawn carts between San Jorge  and San Juan del Sur ; this was the only dry land crossing of the entire gold rush journey. At about the same time, one of filibuster William Walker’s first military defeats took place here.
But it’s hard to compete with La Isla de Ometepe for attention. The magnificent twin-peaked Ometepe rises like a crown from the center of Lake Cocibolca. An intensely volcanic island steeped in tradition and mystery, Ometepe was the ancestral home of the Nahuatl people and today is an alluring destination for travelers, with its sandy beaches, swimming holes, hiking trails, and of course, two breathtaking volcanoes: one hot, one cold (the former remains quite active).
Southwestern Nicaragua does not suffer the same intense, grinding poverty prevalent in the drier lands of the north and west. It rains more in the south, and the rivers flow nearly year-round. The volcanic soils on Lake Cocibolca’s western shore are rich and productive. Cattle graze lazily in immense, lucrative ranches and sugarcane fields drape the valleys south of the foot of Mombacho , one of Nicaragua’s most picturesque peaks.