Parque Nacional Guanacaste (tel. 506/2666-7718 or 2666-5051, or 2661-8150 Sector Pocosol, $10, by reservation only) protects more than 84,000 hectares of savanna, dry forest, rainforest, and cloud forests extending east from Highway 1 to 1,659 meters atop Volcán Cacao.
The park is contiguous with Santa Rosa National Park  (to the west) and protects the migratory routes of myriad creatures, many of which move seasonally between the lowlands and the steep slopes of Volcán Cacao and the dramatically conical yet dormant Volcán Orosi (1,487 meters), whose rain-drenched eastern slopes contrast sharply with the dry plains.
It is one of the most closely monitored parks scientifically, with three permanent biological stations. The Pitilla Biological Station is at 600 meters elevation on the northeast side of Cacao amid the lush, rain-soaked forest. It’s a nine-kilometer drive via Esperanza on a rough dirt road from Santa Cecilia, 28 kilometers east of Highway 1. A 4WD vehicle is essential.
Cacao Field Station (also called Mengo) sits at the edge of a cloud forest at 1,100 meters on the southwestern slope of Volcán Cacao. You can get there by hiking or taking a horse 10 kilometers along a rough dirt trail from Quebrada Grande ; the turnoff from Highway 1 is at Potrerillos, nine kilometers south of the Santa Rosa National Park turnoff. You’ll see a sign for the station 500 meters beyond Dos Ríos (11 km beyond Quebrada Grande).
The road—paved for the first four kilometers—deteriorates gradually. With a 4WD vehicle you can make it to within 300 meters of the station in dry season, with permission; in wet season you’ll need to park at Gongora, about five kilometers before Cacao, and proceed on foot or horseback.
Maritza Field Station is farther north, at about 650 meters on the western side of the saddle between Cacao and Orosi Volcanoes. You get there from Highway 1 via a 15-kilometer dirt road to the right at the Cuajiniquil crossroads. There are barbed-wire gates; simply close them behind you. A 4WD vehicle is essential in wet season. The station has a research laboratory.
From here you can hike to Cacao Biological Station. Another trail leads to El Pedregal, on the western slope of Orosi, where almost 100 petroglyphs representing a pantheon of chiseled supernatural beings lie half-buried in the luxurious undergrowth.
The park is administered from the Guanacaste Regional Conservation Area Headquarters at Santa Rosa.
You can camp at any of the field stations ($2 per day), which also provide Spartan dormitory accommodations on a space-available basis; for reservations, contact the park headquarters in Santa Rosa National Park , which can also arrange transportation.
Cacao Field Station has a lodge with five rustic dormitories for up to 30 people. It has water, but no towels or electricity.
Maritza Field Station is less rustic and has beds for 32 people, with shared bath, water, electricity, and a dining hall.
The Pitilla Biological Station has accommodations for 20 people, with electricity, water, CB radio, and basic meals. Students and researchers get priority. Rates are $15 adult visitors, $10 scientists, $6 students and assistants.