Southeast of San Jose and southeast of San Isidro, the Chirripo National Park has a popular hike up to the highest peak in Costa Rica. The challenging 22km route to the Chirripo summit up 2,520m typically takes about 10 hours and there are refugios for overnight stays. At the summit, you can expect temperatures near freezing at night.
To reach Chirripo National Park from San Isidro, follow the road to the town of San Gerardo de Rivas (about 9km). From San Gerardo de Rivas, head northeast for another 13km into the park passing a church and veering right at the fork. The trailhead should be well marked.
Note: Only 40 visitors a day are permitted into the Chirripo National Park. You will need to call ahead for a reservation.
Overall, Chirripo National Park is the 20th most popular hiking trail of all 20 hikes in Costa Rica.