Thermal Springs and Spas [1]: At Tabacón Hot Springs, one of your enticing hot springs options, you can bathe in steaming waters that tumble from the bowels of Arenal Volcano to cascade through a landscaped garden.
Arenal Waterfall Gardens [2]: Visit this fantastic set of landscaped thermal cascades (and the setting for an episode of The Bachelor) that also features a wild-cat center.
Arenal Volcano National Park [3]: With a symmetrical volcano at its heart, this national park has hiking trails over still-warm lava flows, and the open spaces offer prime wildlife-viewing.
Rancho Margot [4]: This ecologically self-sustaining farm and wildlife rescue center has rustic but endearing accommodations, plus hiking, rappelling, and horseback riding.
Arenal Rainforest Reserve [5]: The aerial tram at this private reserve promises high-mountain rides and staggering vistas. Nature trails and canopy tours provide close-up encounters with wildlife.
Caño Negro Wildlife Refuge [6]: This croc-infested swamp and forest ecosystem is a dream for bird-watchers and wildlife lovers, and a nirvana for anglers to hook tarpon, garfish, and snook.
Tenorio Volcano National Park [7]: Long off the tourist charts, this volcano is a newfound frontier for hiking, including to the jade-colored Río Celeste.
Centro Neotrópico Sarapiquís [8]: This educational center offers a museum of indigenous culture, an archaeological park, and nature trails through the Tirimbina Rainforest Reserve.
Selva Verde [9]: Enfolded by rainforest, this dedicated nature lodge offers instant access to wildlife-rich terrain. Options include guided hikes by day and night, plus canoeing on the Río Sarapiquí.
Isla Las Heliconias [10]: The Dutch owners will guide you on a tour of this beautiful botanical garden. In addition to heliconias, it displays ginger, palms, orchids, bamboo, and other tropical flora.
Links:
[1] http://www.moon.com/destinations/costa-rica/the-northern-zone/la-fortuna-tabacon/thermal-springs-and-spas
[2] http://www.moon.com/destinations/costa-rica/the-northern-zone/la-fortuna-tabacon/arenal-waterfall-gardens
[3] http://www.moon.com/destinations/costa-rica/the-northern-zone/arenal-volcano-and-vicinity/arenal-volcano-national-park
[4] http://www.moon.com/destinations/costa-rica/the-northern-zone/arenal-volcano-and-vicinity/el-castillo/rancho-margot
[5] http://www.moon.com/destinations/costa-rica/the-northern-zone/arenal-volcano-and-vicinity/el-castillo/arenal-rainforest-reserve
[6] http://www.moon.com/destinations/costa-rica/the-northern-zone/los-chiles-and-vicinity/cano-negro-wildlife-refuge
[7] http://www.moon.com/destinations/costa-rica/the-northern-zone/highway-4-upala/tenorio-volcano-national-park
[8] http://www.moon.com/destinations/costa-rica/the-northern-zone/puerto-viejo-de-sarapiqui-and-vicinity/la-virgen-chilamate/centro-neotropico-sarapiqui
[9] http://www.moon.com/destinations/costa-rica/the-northern-zone/puerto-viejo-de-sarapiqui-and-vicinity/la-virgen-chilamate/selva-verde
[10] http://www.moon.com/destinations/costa-rica/the-northern-zone/puerto-viejo-de-sarapiqui-and-vicinity/south-puerto-viejo/heliconia-island