This remarkable expanse of protected wilderness is Nicaragua's biggest biosphere reserve, and makes up more than 14% of Nicaragua’s national territory. It's a challenging place, covered in thick, steamy rainforest bisected by brown rivers, that isn't remotely set up for tourism. With some careful planning, not insignificant expense and no attachment to creature comforts, it is possible to visit, however.
Come prepared: someone in your group (don’t do this alone) should speak a fair amount of Spanish, and you should consider taking malaria pills for longer adventures. Water-purification technology is necessary for most of the reserve. But the real key to access is persistence – you can get in, just don’t count on it happening on your timetable, and expect to be following leads like: ‘find Jaguar José at the pulpería near the empalme of (something unpronounceable); he’s got a truck that can get through.’
During the reserve’s February-to-April dry season, rivers (read: the freeway system) may be too low to travel, unless you help carry the canoe around the rapids. Luckily, it’s usually raining, and some spots (for instance, the Río Waspuk region) get 3200mm of rain per year – regular roads may be impassable most of the year. Temperatures average a sweaty 26.5°C (80°F), but bring a fleece for Cerro Kilambé (1750m).
The easiest access to the Reserve de Biosfera Bosawás is from Siuna via the Parque Nacional Saslaya. Head to the ranger station, 3.5km from the community of Rosa Grande, where you'll register and contract a guide for the trek to Piedra Colorada. You’ll overnight by a pine-shaded lagoon and in the morning begin the three-day climb to Cerro El Toro (1652m), or an overnight trip up El Revenido. A rolling trail circumnavigates both peaks, and can be done in one day.
Hormiguero is another national-park gateway. From the ranger station at the trailhead, it’s a five-hour hike to Camp Salto Labú, with a stunning swimming hole that has a cave, canyons and petroglyphs. From here, you can also begin a four-day trek to the top of Cerro Saslaya (1651m). Bring a sleeping bag, tent and water-purification for both treks.