WANT TO TAKE a trip to the woods and be sure of encountering wildlife you don't see every day? Start your trip indoors at one of the many nature centers staffed by professional park naturalists throughout the area. The centers, located in some of the county, national and regional parks, serve as microcosms of the outdoor environments in which they sit.

Almost all serve as starting points for nature trails and give printed guides for identifying the species and ecosystems you'll encounter in the parks. You can examine live or dead specimens of the animals that dwell in the surroundings. Return to the center after a hike and a ranger or guidebook can help you identify any unusual mammals, birds, bugs or plants you may have found or answer any other questions.

Many centers feature libraries and special hands-on exhibits for children. The centers all offer nature hikes and programs. (Call for schedules.) Many also offer classes for preschoolers through adults. They will gladly arrange special programs for groups of scouts, schoolchildren, seniors and others -- but call ahead.

Note that some centers may keep shorter winter hours, but not before you can watch the change in seasons. Here, in a nutshell, is a rundown on some of the local programs: THE DISTRICT

ROCK CREEK NATURE CENTER --

In Rock Creek Park, 5200 Glover Rd. NW. 202/426-6829. Open 9 to 5 daily. Exhibits are designed around the flora and fauna found in the park, "like an orientation to going out in the park and finding these things for yourself," says supervisor Dave Smith. Two trails lead through the woods around the center; you can explore on your own or on ranger-led tours given on weekends. Max the Owl has been a popular attraction since his wing was broken by a car 17 years ago -- though he's not very friendly. The center also includes the nation's only Park Service planetarium, offering weekend shows at 1 p.m. for ages four and up, and more sophisticated shows at 4 p.m. for ages seven and up. VIRGINIA

PRINCE WILLIAM FOREST PARK VISITORS CENTER --

Off Route 619 (Joplin Road). From I-95 take Exit 50B west. 703/221-7181.The new nature center near the park entrance is open 8:30 to 5 daily. Admission to the park is $3 per car. Exhibits, talks, hikes and videos focus on the park and the land's history (including how the Civilian Conservation Corps built the park in the 1930s), the National Park Service itself, Indian life, farmland and machinery from the Old Pyrite Mine in the park. (A two-mile hike will take you to the mine ruins.) A "touch-me" table for children includes deer antlers and an inactive beehive. The staff will show nature films on request. The 35 miles of hiking trails include a quarter-mile paved route for the disabled, with audio boxes explaining the sites along the way.

GULF BRANCH NATURE CENTER --

LONG BRANCH NATURE CENTER --

625 S. Carlin Springs Rd., Arlington. 703/358-6535. Open 10 to 5 Tuesday through Saturday and 1 to 5 Sundays. Long Branch features a smell exhibit. Pick up a jar and take a whiff of the scents of deer, fox or a variety of wildflowers. You can also see a litter of baby turtles as well as a collection of grown-up turtles, snakes and assorted reptiles and fish in cages and an indoor pond. Meet Jonesey the baby opossum, who the nature center adopted last month after his mother was run over by a car -- he lets people pet him. Wooded trails around the center lead to two ponds and the only swamp in Arlington.

POTOMAC OVERLOOK NATURE CENTER --

HIDDEN OAKS NATURE CENTER --

Annandale Community Park, 4020 Hummer Rd., Annandale. 703/941-1065. Open Mondays and Wednesday through Friday 9 to 5 and noon to 5 weekends. The 21-year-old nature center features tanks of snakes, toads, turtles and fish; hands-on artifacts; and an exhibit on the natural history of the county. Nature films are shown at 3 on weekends.

HIDDEN POND NATURE CENTER --

Hidden Pond Park, 8511 Greeley Blvd., Springfield. 703/451-9588. Open 9 to 5 Mondays and Wednesday through Friday, and noon to 5 weekends. See and learn about the pond and amphibians that live in it. The center overlooks the two-acre Hidden Pond, made in the 1950s by the former land owners. You can touch the box turtles and quiz yourself on nature, then take a walk on the self-guided nature trail.

WALNEY VISITOR CENTER --

Ellanor Lawrence Park, 5040 Walney Rd., Chantilly. 703/631-0013. Open 9 to 5 Mondays and Wednesday through Thursday and noon to 5 weekends. This nature center is set in a 210-year-old farmhouse and features displays on the history and nature of the 640-acre park. Visitors can handle an assortment of well-behaved reptiles. Kiddies' Corner also allows handling of park artifacts, including birds' nests, pine cones and logs chewed by beavers. Many of the exhibits are at preschoolers' eye level.

RAMSEY NATURE CENTER --

CLEARWATER NATURE CENTER --

Louise Cosca Regional Park, 11000 Thrift Rd., Clinton. 301/868-1397. Open 8:30 to 5 weekdays, 9 to 4 Saturdays and 11 to 4 Sundays and holidays; closed Sundays in winter. The building, made out of lava rock, features a collection of stuffed animals and skins, plus a live rabbit and reptiles, some of the latter in an indoor pond. Outside, you can take a look at the Suitland Bog (a garden for meat-eating plants), explore the greenhouse or walk to a 15-acre lake.

30TH STREET NATURE CENTER --

WATKINS NATURE CENTER --

Robert Watkins Regional Park, 301 Watkins Park Dr., Upper Marlboro. 301/249-6202. Open 9 to 5 weekdays, 9 to 4 Saturdays and 11 to 4 Sundays. The nature center features a stocked indoor pond and what park Nature Facilities Supervisor Sidney Jacobs calls "probably the biggest bullfrogs this side of the Mississippi." Sometimes the naturalists will let you feed them worms or slugs. Barnie the Barn Owl has lived in a small barn in the center since he was mistakenly taken out of a nest 10 years ago. You can also see two screech owls adopted by the center after they suffered injuries in the wild. If the owls won't sing for you, you can hear owl voices on tape. And you can view a beekeeping exhibit. A five-minute walk to the park takes you to Old Maryland Farm, which features pigs, goats, sheep, chickens, ducks, turkeys and rabbits as well as organically grown crops. The barn has exhibits on organic farming and conservation.

BROOKSIDE NATURE CENTER --

Wheaton Regional Park, 1400 Glenallen Ave., Wheaton. 301/946-9071. Home to a few wounded birds, the center also features aquariums full of snakes, salamanders, turtles and fish, and a variety of stuffed wildlife. In Discovery Niche, children can smell herbs and try to figure out what they are. The library has nature books for youngsters and hands-on artifacts and puppets (turn the tadpole inside out and it becomes a frog). If you shut out the lights in one corner you can view the constellations on the ceiling. A short hike through wooded trails takes you next door to Brookside Botanical Gardens, which is always full of color. Nature flicks are shown Saturdays at 11, 1 and 3; Sundays at 2 and 4.

HAWK'S REACH NATURE CENTER --

Little Bennett Regional Park, 23701 Frederick Rd., Clarksburg. 301/972-9458. Open to the public 1 to 5 Saturdays only through October. (The center was converted from the campground store in the middle of the campground and the limited hours are to prevent the public from disturbing campers.) The center includes an extensive collection of reptiles, amphibians and insects. Exhibits challenge children to solve nature puzzles. At the bird table, for instance, visitors are given all the raw materials to build a bird's nest and invited to try, noting that they have the advantage of having hands that birds don't. "It gets across the idea that this is not as easy as it looks," says Park Naturalist Denise Gibbs. A butterfly and hummingbird garden is outside.

MEADOWSIDE NATURE CENTER --

Rock Creek Regional Park, 5100 Meadowside Lane, Rockville. 301/924-4141. Open 9 to 5 Tuesday through Saturday and 1 to 5 Sundays. The center features Legacy of the Land, an indoor forest with a working waterfall, a small pond and a cave children can crawl through. The Legacy of the People exhibit consists of replicas of an Indian hut and a cabin visitors can walk through. The cabin includes copies of toys of bygone eras. Curiosity Corner features snakes, fish, turtles and a microscope. Once outside, you can hike to Lake Frank.

Charles Pekow last wrote for Weekend about area bike trails.