Volcán Turrialba (3,329 meters), the country’s most easterly volcano, was very active during the 19th century, but had slumbered peacefully since.
In 2001, it showed signs of activity after 135 years of dormancy. Then, BOOM! On January 6, 2010, the volcano erupted.
By historical standards it wasn’t an earth-shattering eruption, but ash and gas clouds reached skyward and high winds from the east spread ash across the Meseta Central. The activity continues.
It can be very cold and rainy up here—bring sweaters and raingear. There are no ranger stations at Parque Nacional Volcán Turrialba; hence access is free. Contact SINAC in San José  (tel. 506/2268-8091).
A paved (but badly eroded) road winds steeply north from Santa Cruz, about 12 kilometers north of the town of Turrialba , to Finca Central; it’s a rugged three kilometer drive by four-wheel drive from there.
An alternate route for 4WD vehicles only is via the Irazú Volcano National Park  road; turn off two kilometers below the park ranger station (signed for Volcán Turrialba Lodge).
You can also hike from the hamlet of Santa Teresa, reached by direct bus or car from Cartago via Pacayas, on the southwestern slope. The trail climbs through cloud forest to the summit, which features three craters, a mirador (lookout point), and guardhouse topped by an antenna. A trail at the summit leads to the crater floor; another circumnavigates the crater (there are active fumaroles on the western side).
Perfect for bird-watchers and hikers, Volcán Turrialba Lodge (tel. 506/273-4335, www.volcanturrialbalodge.com , from $50 s/d including breakfast and tax) is set magnificently in the saddle between Irazú and Turrialba Volcanoes at 2,800 meters elevation, about three kilometers north of Esperanza and eight kilometers northwest of Santa Cruz. The rustic lodge—on a working farm—has 18 simple yet comfy rooms with private baths. Meals are cooked over a wood fire and served in a cozy lounge heated by a woodstove. Guided hikes and horseback rides are offered.