Trailing away from Granada's southern waterfront is the 354-island archipelago known as Las Isletas, formed by a volcanic eruption from nearby Mombacho over 10,000 years ago. These tiny jungle islands are literally parts of the mountain blown into the lake during a massive eruption. They are now lush mounds that host mini-monkey sanctuaries, humble campesino huts and lavish mansions, and attractions such as an island cemetery and an old Spanish fort called Fortín San Pablo. It is a popular 1-day excursion, and boats leave frequently from the southern end of the Complejo Turístico Cocibolca. You can go there independently by taking a taxi or walking a half-hour south along the shore of the Centro Turístico until you reach a building with small pontoons and boats that leave as soon as they fill up. Or take a tour with any of the travel operators in the city center.
I found the conventional tour of the islands to be a huge disappointment. Every rock seemed to be sporting a real-estate sign, and the motorboats scared away all wildlife. The quality of restaurants in the touristy parts of the islands leaves a lot to be desired, too, with limited menus and outhouse restrooms (bring your own toilet paper). The true way to enjoy the islands, and avoid the hordes, is to get up early and go farther out in a kayak or private boat. Aquatic birds such as egrets, herons, and cranes can be spotted in the early morning or evening, as well as kingfishers and cormorants. You soon realize that the islands are each a community onto itself with a school, cemetery, restaurants, and bars on individual mounds of basalt topped with tall ceiba trees and mango orchards. Though wealthy weekenders have now started buying up their own private slices of paradise (usually on the north side of the archipelago), the vast majority of the islanders are dirt poor and survive on fishing guapote and mojarra from the dark waters on the south side. This is by far the most interesting part to see. Conventional agencies offer short, unsatisfactory tours of the islands. For something more thorough and interesting, try agencies such as Nahual Tours (tel. 505/8988-2461; www.nahualtours.com) and Inuit Kayaks.
Lago de Nicaragua -- The Sweet Sea
Standing on the dark, breezy shore of Lago de Nicaragua, you might be forgiven for thinking that this was always just a peaceful backwater. In fact, you're standing on a momentous piece of ground whose formation altered the Americas forever. Five million years ago the earth rose up with volcanic might around and within this body of water, forming an 8,264-sq.-km (3,191-sq.-mile) flood plain. Shifting tectonic plates and molten lava conspired to create what is now the narrow Central American isthmus, splitting the Pacific from the Atlantic and connecting two great continents. This new land bridge allowed wildlife and vegetation, and eventually people (a mere 30,000 years ago), to travel between the two landmasses.
Lago Cocibolca (as it is also known) is the largest lake in Central America and only slightly smaller than Lago Titicaca. It is much lower and shallower than its Bolivian counterpart, averaging 26m (85 ft.) in depth and lying just 32m (105 ft.) above sea level.
The Spanish called it Mar Dulce (Sweet Sea), and you can see why, as it is teeming with wildlife of the most unusual kind, including prehistoric garfish, sawfish, and tarpon. Perhaps the most unusual is the freshwater shark that confounded scientists for years. Eventually, they discovered it is a Caribbean bull shark that travels up the rapids of the San Juan River, much the same as salmon jump upriver when migrating. That same river gave Granada the huge historical advantage of being an Atlantic port city despite, somewhat paradoxically, being closer to the Pacific.
With its 450 volcanic islands, some of which were important religious sites for the indigenous tribes who worshiped, sacrificed, and practiced cannibalism on them, the lake is a must-see when traveling through Nicaragua. The least you can do is tour Las Isletas near Granada or the twin volcanoes of Ometepe Island. The truly adventurous make it to the magical monument island of Zapatera or the artistic archipelago of Solentiname.
Alarmingly, the lake's ecosystem is under threat. The sharks are long gone, and there are serious concerns about the pollution from fish farms, raw sewage from settlements, and effluent from factories. Sadly, the sweet sea may not be so sweet for much longer, and Central America will be a lesser place for it.