Picture-perfect Lake Arenal might have been transplanted from the English Lake District, surrounded as it is by emerald-green mountains. The looming mass of Volcán Arenal  rises over the lake to the east.
About 2–3 million years ago, tectonic movements created a depression that filled with a small lagoon. In 1973, the Costa Rican Institute of Electricity (ICE) built an 88-meter-long, 56-meter-tall dam with HEP station at the eastern end of the valley, creating a narrow 32-kilometer-long reservoir covering 12,400 hectares.
High winds whip up whitecaps, providing thrills for wind- and kite-surfers, and powering huge turbines that stud the mountain ridge southwest of the lake. (Warning: Crocodiles have been seen in the lake in recent years. Don’t ask me how the heck they got there!)
The only town is Nuevo Arenal, a small pueblo on the north-central shore, 32 kilometers northeast of Tilarán, immediately west of the Guanacaste-Alajuela provincial boundary. It was created in 1973 when the artificial lake flooded the original settlement, and now occupies a ridge (prime real estate) with gorgeous views. This is the only place to gas up and use an ATM.
The lake is easily reached from La Fortuna  (20 kilometers east of the dam), or from Cañas  on the Pan-American Highway via Tilarán. The paved road swings around the north and west side of the lake, linking the two towns. The section east of Nuevo Arenal is backed by thick rainforest and is one of the prettiest drives in Costa Rica, with a fistful of eclectic restaurants and bed-and-breakfasts dotting the route.
Animals such as coatis are often present, begging for food. (Don’t feed the wildlife!) I’ve even seen a peccary crossing the road. Landslides are a frequent occurrence and often close the road east of Nuevo Arenal for days at a time; at best, expect some washed-out sections.
A dirt road that begins just east of Hotel La Mansion Inn leads over the cordillera to Venado Caverns . Another road leads north from just west of Nuevo Arenal with San Rafael de Guatuso; a fork leads past Lake Coter (a small lake) five kilometers northwest of Nuevo Arenal.
On the south side, a road is paved as far as Tronadora, beyond which it turns to dirt and eventually peters out. You cannot get through to El Castillo  or La Fortuna.
This area has seen a boom in the gringo population, many of whom have bought land and opened up bed-and-breakfasts and other businesses.
Arenal Hanging Bridges (tel. 506/2290-0469, www.hangingbridges.com , 8 a.m.–4:30 p.m. daily, $22 adults, $17 seniors, $12 students), within a 250-hectare reserve immediately east of the dam, provides a marvelous entrée to forest ecology as you follow a three-kilometer self-guided interpretive trail with 15 sturdy bridges (some up to 100 meters long) suspended across ravines and treetops. Guided tours include an early-morning bird-watching tour ($25). You get great volcano views. Last entrance is at 3:30 p.m.
Maverick’s (tel. 506/2694-4282), in Nuevo Arenal, cranks it up on Saturday nights. Entry is $2 when live bands play. A U.S.-run sports bar, Longhorn’s Bar & Grill (tel. 506/2695-5663, http://site.longhornbarandgrill.com , 4–9 p.m. Thurs.–Sat., 11 a.m.–9 p.m. Sun., 4–9 p.m. Mon.), at the Cinco Esquinas (the junction of the road to Tronadora), will appease homesick gringos pining for NFL football.
Serious sudsters should make a beeline to Hotel Tilawa (tel. 506/2695-5050, www.hotel-tilawa.com , 6:30–10 p.m. daily), where an impressive home-brew set up, with copper vats on view, delivers even more impressive beers on tap. I enjoyed an awesome pale ale and hefeweizen ($5 for 12 oz., $20 pitchers).
Monica’s Roadhouse (tel. 506/2695-5309), one kilometer north on the Tronadora road, was closed for remodeling at last visit, but owner John Van DeCamp expects to open his popular lake-view bar (famous for its Wednesday gringo nights) with a dance floor.
The yang to Monica’s yin is the Pukka Waiku Disco (formerly Full Moon), a farmhouse-themed place—think saddles and ox-yokes for decor—good for a knees-up local style. The disco to the rear is a rambling stone-lined affair that packs in locals on Saturday nights.
There’s a canopy tour ($55) at the Lake Coter Ecolodge (tel. 560/2289-6060, www.ecolodgecostarica.com ), which also offers hiking ($19), horseback rides ($24), canoeing (and kayaking ($22 each), and water sports. The Establo Arenal (tel. 506/2694-4434, www.thestablearenal.com ), about three kilometers west of Nuevo Arenal, rents horses and has a horse-riding school. Hotel Tilawa (tel. 506/2695-5050) has a skateboard ($4) and BMX ($6) park.
In the morning the lake can look like a mirror, but the calm is short-lived. More normal are nearly constant 30- to 80-kph winds, which whip up whitecaps and turn the lake into one of the world’s top windsurfing spots. Swells can top one meter. Forty-kph is the average winter day’s wind speed. November, December, and January are the best months for windsurfing; September and October the worst.
The Tilawa Viento Surf Center (tel. 506/2695-5050, www.windsurfcostarica.com ), on the southwest shore, focuses on beginners ($35 per two-hour lesson, $60 per hour thereafter) and has kayaks as well as board rental ($45 half-day). Englishman Peter Hopley runs the more impressive Tico Wind Surf Center (on the western shore, tel. 506/2692-2002, www.ticowind.com , 9 a.m.–6 p.m. daily Nov.–Apr.). Peter uses state-of-the-art equipment, has a great lineup of gear, and offers instruction in several languages. One-hour beginner lessons cost $50; a full nine-hour course costs $480. Board rentals are from $15 per hour, $42 half-day. You need a 4WD vehicle for access.
Paradise Adventures (tel. 506/8856-3618, www.paradise-adventures-costa-rica.com ) spices up the experience with wakeboarding behind speedboats—it’s like snowboarding on water. Owner Jonny T brings in world champs as instructors.
Arenal Kayaks (tel. 506/2694-4366, www.arenalkayaks.com ), about one kilometer east of Nuevo Arenal, rents kayaks and has guided trips using hand-crafted wooden kayaks made on-site.
The lake is stocked with game fish—guapote, machaca, and (for lighter tackle enthusiasts) mojarra. Most of the hotels hereabouts offer fishing tours, as does Capt. Ron’s Lake Arenal Fishing Tours (tel. 506/2694-4678, www.arenalfishing.com ), in Nuevo Arenal.
The Rain Goddess is a deluxe 65-foot live-aboard vessel that operates three-hour lake tours daily at 4 p.m. ($70) with dinner optional. Book with local tour operators.
Buses (Garaje Barquero, tel. 506/2232-5660) depart San José  for Nuevo Arenal from Calle 16, Avenidas 1/3, at 6:15 a.m., 8:40 a.m., and 11:30 a.m. daily. Buses depart Cañas  for Tilarán and Nuevo Arenal at 7:30 a.m. and 3 p.m. daily ($0.50); from Tilarán  at 8 a.m. and 4:30 p.m. daily; and from La Fortuna  to Tilarán via Nuevo Arenal at 7 a.m. and 12:30 p.m. daily.
An express bus departs Nuevo Arenal for San José via Ciudad Quesada  at 2:45 p.m. daily; additional buses depart for Ciudad Quesada at 8 a.m. and 2 p.m. daily. A bus marked Guatuso also departs Arenal at 1:30 p.m. daily for San Rafael, Caño Negro , and Upala in the northern lowlands.
Water-taxis depart the dam at the east end of the lake and run to Nuevo Arenal, El Castillo, and Tronadora.