The 2,295-hectare Parque Nacional Barra Honda (tel. 506/2659-1551 or 2659-1099, act.barrahonda [at] sinac [dot] go [dot] cr, 8 A.M.–4 P.M. daily, $10), 13 kilometers west of the Río Tempisque, is a rugged upland area known for its limestone caverns dating back 70 million years (42 caverns have been discovered to date). Skeletons, utensils, and ornaments dating back to 300 B.C. have been discovered inside the Nicoya Cave. The deepest cavern thus far explored is the 240-meter-deep Santa Ana Cave, known for its Hall of Pearls full of stalactites and stalagmites.
The only caverns open to the public are Terciopelo Cave (children must be 12 or over), with three chambers reached via an exciting 30-meter vertical ladder, then a sloping plane that leads to the bottom, 63 meters down; and La Cuevita. Within, Mushroom Hall is named for the shape of its calcareous formations; the Hall of the Caverns has large Medusa-like formations, including a figure resembling a lion’s head. And columns in The Organ produce musical tones when struck.
Some of the caverns are frequented by bats, including the Pozo Hediondo (Fetid Pit) Cave, which is named for the quantity of excrement accumulated by its abundant bat population. Blind salamanders and endemic fish species have also evolved in the caves. Caverna Nicoya contains pre-Columbian petroglyphs.
Above ground, the hilly dry-forest terrain is a refuge for howler monkeys, deer, agoutis, peccaries, kinkajous, anteaters, and many bird species, including scarlet macaws. The park tops out at Mount Barra Honda (442 m), which has intriguing rock formations and provides an excellent view of the Gulf of Nicoya. Las Cascadas are strange limestone formations formed by calcareous sedimentation along a riverbed.
Cave descents are allowed 7:30 A.M.–1 P.M. daily May–November, and until 2 P.M. daily December–April, except Holy Week ($36 s, $52 d four hours, including entrance, guide, and cave equipment; the price varies depending on number of participants).
For cave descents, you must be accompanied by a guide from the Asociación de Guías Ecologistas de Barra Honda, which also has guided walks ($10 pp) plus nighttime tours ($8 pp, three-person minimum, beginning at 4 P.M.) in dry season. Budget at least four hours to visit the caves. You can drive to about 1.5 kilometers beyond the park entrance, after which you’re on foot: it’s hot and steep, and there are mosquitoes.
Reservations are required for the Sendero Las Cascadas, which leads to waterfalls; guided tours only.
There’s a campsite ($2 pp) at the ranger station, which also has simple cabins for volunteers willing to help with trail maintenance and other projects. It has basic showers and toilets plus picnic tables and water. At last visit, meal service was being planned.
One kilometer before the park entrance, Hotel Barra Honda (tel. 506/2659-1003, $15 s/d) is set in spacious tree-shaded grounds and has a simple open-air restaurant. It offers horseback rides. The 10 basic cabins have fans and spacious modern bathrooms.
Of similar standard, Las Cavernas Tourist Lodge (tel. 506/2659-1574, fax 506/2659-1573, $12 pp), 400 meters from the park entrance, has five bare-bones rooms with cold-water private bathrooms and a delightful cowboy-style restaurant and bar decorated with yokes and saddles. It has a small pool.
The turnoff for the Nacaome (Barra Honda) ranger station is 1.5 kilometers east of Puerto Viejo and 15 kilometers west of the Tempisque Bridge. From here, an all-weather gravel road leads via Nacaome, all the while deteriorating (4WD recommended); signs point the way to the entrance, about six kilometers farther via Santa Ana.
A Tracopa-Alfaro (tel. 506/2222-2666) bus from San José  to Nicoya  will drop you at the turnoff for the park; Las Cavernas will send a pickup by prior arrangement. A bus departs Nicoya for Santa Ana and Nacaome at 12:30 P.M. daily, plus 4 P.M. on Monday, Wednesday, and Friday; you can walk to the park entrance. You can also enter the park from the east via a dirt road (from Quebrada Honda, off Highway 21 immediately east of Nicoya township.