Fabulously scenic Highway 164 leads northeast from Bagaces  and climbs steadily up the western shoulder of Miravalles Volcano (2,028 meters), enshrined within the Miravalles Protected Zone (Zona Protectora Miravalles). The almost perfectly conical volcano is the highest in the Cordillera de Guanacaste.
The western slopes or Miravalles are covered with savanna scrub; the northern and eastern slopes are lush, fed by moist clouds that sweep in from the Caribbean. The southern slopes are cut with deep canyons and licked by ancient lava tongues, with fumaroles spouting and hissing like mini Old Faithfuls.
The forests, replete with wildlife, are easily accessed from the road. However, there are no developed trails or facilities for tourists, and no ranger station.
Highway 164 runs via the village of Guayabo, 21 kilometers north of Bagaces (it has a bank, Internet café, and several cabinas). It is paved as far as Aguas Claras and extends beyond to the hamlet of San José in the northern lowlands. If souvenir shopping, call in at Galería Tony Jiménez (tel. 506/8821-8358, www.tonyjimenez.com ), midway between Guayabo and Aguas Claras.
A loop road from Highway 164 leads east via the community of La Fortuna de Bagaces to Las Hornillas (Little Ovens), an area of intense bubbling mud pots and fumaroles expelling foul gases and steam. Here the Costa Rican Institute of Electricity (ICE) harnesses geothermal energy for electric power, with two plants that tap the superheated vapor deep within the volcano’s bowels. You can visit the main Planta Miravalles geothermal plant (tel. 506/2673-1111, ext. 232), about two kilometers north of Fortuna, by appointment.
The touristy Centro Turístico Yökö (tel. 506/2673-0410, www.yokotermales.com , $5) is a recreation park amid lawns one kilometer west of Las Hornillas, with five clean thermal pools (ranging 30–50°C) set amid 13 hectares; one even has a water slide and an artificial cave that serves as a sauna. Massage is offered, as are horseback rides ($15, four hours). Nearby, Centro Turístico Termomanía (tel. 506/2673-0233, $5) competes; the highlight is the hornillas—bubbling mud pools and fumaroles—immediately adjacent to the property. It’s totally unguarded and very dangerous—keep your distance!
At Aguas Claras, you can turn west (4WD required) to visit Finca La Anita (tel. 506/8388-1775, www.fincalaanita.org ) organic farm.
The prime spot to enjoy the volcanic activity is this mesmerizing facility (tel. 506/8839-9769, www.hornillas.com , 8 A.M.–5 P.M. daily, $25), a “walkable live crater” two kilometers southeast of the ICE geothermal plant.
Here, boardwalks lead through the crater itself, with mud pools and fumaroles hissing and bubbling all around. You can walk around at will and even take a therapeutic bath in a warm mud bath, while a two-hour guided tour ($40) includes a tractor tour to waterfalls. A highlight is the 100-meter-long water slide. It has showers and toilets.
The Miravalles Volcano Adventure Center (tel. 506/2673-0469, www.volcanoadventuretour.com ) has a canopy tour (8 A.M.–3 P.M. daily, $30) seven kilometers north of Guayabo. It has 11 zip lines and 14 platforms, plus hiking trails.
You can camp on the lovely grounds of the Miravalles Volcano Adventure Center ($5 pp), which also has four very simple cabins ($35) with modern bathrooms and a rustic restaurant.
Centro Turístico Yökö (tel. 506/2673-0410, www.yokotermales.com , $40 s, $60 d) has 12 spacious cabins with verandas with volcano views, plus ceiling fans and large private bath and walk-in showers with thermal water. It has a restaurant with TV. Rates include breakfast and use of facilities. Centro Turístico Termomanía (tel. 506/2673-0233) competes, less impressively.
New in 2010, the more upscale Ailanto Wellness Resort & Spa (tel. 506/8345-3741, www.ailantoresort.com ), above La Fortuna , has a bed-and-breakfast within a private gated community with private villas and condominiums. The bed-and-breakfast is a modern neo-colonial-style manse with four apartment-style rooms. Its spa features three indigenous-style sweat lodges and offers yoga and meditation. It plans to open a churrasquería, or Argentinian-American grill serving “cowboy chow.”