Pictures of hotels lining the shores of Waikiki Beach and canyons of tall buildings in downtown Honolulu have given Oahu a bad rap. The island is much more than an urban concrete jungle or a tropical Disneyland blighted by overdevelopment; it's also a haven for the nature lover and outdoor enthusiast. With year-round temperatures in the upper 70s, and miles of verdant unspoiled landscape, Oahu is perfect for outdoor activities of all kinds, including hiking, golf, tennis, biking, and horseback riding. But the island's waters, which also enjoy year-round temperatures in the upper 70s, are where the majority of residents and visitors head for relaxation, rejuvenation, and recreation. Locals don't think of their island or state boundaries as ending at land's edge -- rather, they extend beyond the reefs, well out into the ocean.

Bicycling

Bicycling is a great way to see Oahu. Most streets here have bike lanes. For information on biking trails, races, and tours, check out the Bike Hawaii website or tel. 877/682-7433. For information on bikeways and maps, contact the Honolulu City and County Bike Coordinator (tel. 808/768-8335).

If you're in Waikiki, you can rent a bike for as little as $10 for a half-day and $20 for 24 hours at Big Kahuna Rentals, 407 Seaside Ave. (tel. 888/451-5544 or 808/924-2736). On the North Shore, for a full-suspension mountain bike, try Raging Isle, 66-250 Kamehameha Hwy., Haleiwa (tel. 808/637-7707), which rents bikes for $40 to $60 for 24 hours.

For a bike-and-hike adventure, call Bike Hawaii (tel. 877/682-7433 or 808/734-4214); this company offers a variety of group tours, including the Downhill Coasting Ride, which gives you a bird's-eye view of Oahu from 1,800 feet above Waikiki. The tour includes coasting down 5 miles of paved mountain road with scenic views above Waikiki, Honolulu, and Manoa Valley. Listen to the songs of birds, the wind through the trees, and learn about the culture, plants, and geology of the Hawaiian Islands. After that, leave your bike for a 2-mile round-trip hike to a 200-foot waterfall. The 9am-to-3pm trip includes van transportation from your hotel, lunch, bike, helmet, snacks, water bottle, and guide ($96 adults and $75 children under 14).

If you'd like to join club rides, contact the Hawaii Bicycle League (tel. 808/735-5756), which offers rides every weekend, as well as several annual events. The league can also provide a schedule of upcoming rides, races, and outings.

Glider Rides

Imagine soaring through silence on gossamer-like wings, a panoramic view of Oahu below you. A glider ride is an unforgettable experience, and it's available at Dillingham Air Field, in Mokuleia, on Oahu's North Shore. The glider is towed behind a plane; at the proper altitude, the tow is dropped and you (and the glider pilot) are left to soar in the thermals. Three costs are involved in a glider ride: plane rental fee, instructor fee, and towing fee. We recommend Mr. Bill at Honolulu Soaring [ST] (tel. 808/637-0207); he's been offering piloted glider rides since 1970. Rates start at $59 for 10 minutes for just one passenger (and go up to $178 for 60 min.).

Hang Gliding

See things from a bird's-eye view (literally) as you and your instructor float high above Oahu on a tandem hang glider. North Shore Hang/Para Gliding, at the Dillingham Air Field (tel. 808/381-4296), offers the opportunity to try out this daredevil sport. A tandem lesson of ground school plus 30 minutes in the air costs $175.

Horseback Riding

You can gallop on the beach at the Turtle Bay Resort, 57-091 Kamehameha Hwy., Kahuku (tel. 808/293-8811; bus no. 52 or 55), where 45-minute rides along sandy beaches with spectacular ocean views and through a forest of ironwood trees cost $50 for adults and $30 for children 7 to 12 (they must be at least 4 ft., 4 in. tall). Romantic evening rides are $80 per person. Advanced riders can sign up for a 60-minute trot-and-canter ride along Kawela Bay ($100).

Skydiving

Everything you need to leap from a plane and float to earth can be obtained from SkyDive Hawaii, 68-760 Farrington Hwy., Wahiawa (tel. 808/637-9700). A tandem jump (where you're strapped to an expert who wears a chute big enough for the both of you) costs $225 (check the website for a coupon that gives you $75 off this rate). No doubt about it -- this is the thrill of a lifetime. (Although, as SkyDive's website warns, "Skydiving is extremely dangerous.")

Tennis

Oahu has 181 free public tennis courts. To get a complete list of all facilities or information on upcoming tournaments, send a self-addressed, stamped envelope to Department of Parks and Recreation, Tennis Unit, 650 S. King St., Honolulu, HI 96813. In Waikiki, if you want to check on the Diamond Head courts, 3908 Paki Ave., across from the Kapiolani Park, call tel. 808/971-7150. The courts are available on a first-come, first-served basis; playing time is limited to 45 minutes if others are waiting.

If you're staying in Waikiki, try the Wikiki Tennis Court and Lessons at the Aqua Marina Hotel, 1700 Ala Moana Blvd. (tel. 808/551-9438; bus no. 19 or 20), which has one lighted court (9am-9pm daily), with court rental for $10 per person per hour and racket rental for $5 per person per day. Private lessons are $60 per hour, and semi-private instruction is $75 per hour for two or more persons.

If you're on the North Shore, head to the Turtle Bay Resort, 57-091 Kamehameha Hwy., Kahuku (tel. 808/293-8811; bus no. 52 or 55), which has 10 courts, four of which are lit for night play. You must reserve the night courts in advance; they're very popular. Court time is $10 per person (complimentary for guests); equipment rental and lessons are also available.