Yesterday's Weekend section gave an incorrect address for the Washington Area Bicyclist Assocation and an incorrect telephone number of the Potomac Area Council of America Youth Hotels. The address for both organizations is 1520 16th Street NW; the phone number for the Potomac Area Council is 462-5780.

Few cities can rival Washington's network of bike paths.

Three of the best are the trail along Beach Drive in Northwest Washington and Montgomery County, the George Washington Parkway-Mount Vernon bike path in Virginia and the C&O Canal towpath.

The Beach Drive path extends from Knowles Avenue in Kensington to Memorial Bridge, more than 20 miles. An asphalt track five to six feet wide, it mainly parallels the course of Rock Creek. The terrain is mostly level, with a few hills as a challenge.

Starting at Knowles Avenue, the trail winds in and out of woods, meadows and glades on its way to East-West Highway. East of Connecticut Avenue, there's a par course for a more holistic approach to exercise.Farther along, the trail passes under a picturesque railroad trestle and, later, in front of Meadowbrook Stables.

Here, you may continue on the trail, which is packed gravel for a mile or two until it hits Wise Road, or continue to follow Beach Drive in the roadway until Bignham Drive, where it rejoins the paved bike path.

On Sundays, when the Park Service closes the section of Beach Drive from Military Road to Broad Branch Road to all motor vehicles, riding conditions are superior. This is a beautiful, canyon-like stretch of road that renders one oblivious to the presence of civilization.

Past Pierce Mill, the road is again closed to traffic on Sundays. From here the trail winds along, crossing several low water bridges and on past the National Zoo. Immediately past the zoo is the most hazardous part of the trail: Here riders must dismount and walk their bikes over a bridge on an extremely narrow sidewalk. At Calvert Street, there's another par course and a grassy field that's a favorite of sunbathers -- and of riders who like to watch sun bathers.

From here on it's smooth sailing (barring a few potentially dangerous street crossings) down past the Watergate and the Kennedy Center to Memorial Bridge, where riders may link up with the many small roads and sidewalks that interconnect the various monuments and the Mall.

Two cautions about this trail: First, its surface can be slippery when it has leaves on it or is wet; second, it's very popular. Joggers, who long ago replaced dogs as a cyclist's worst enemy, are plentiful and are notorious road hogs. Take care to avoid these waffle-soled menaces, as they are likely to pick the worst places to weave into the unsuspecting rider's path. After all, if a cyclist and jogger do collide, all the jogger has to worry about are bruises, lacerations and possible fractures, while a cyclist can suffer the much worst fate of damaging his bike.

Another very popular bike trail is the George Washington Parkway-Mount Vernon trail, which runs from Memorial Bridge to Mount Vernon in Virginia, almost 16 miles.The terrain is level with only one hill of any consequence.

This is one of the best-maintained trails in the area, and most of it has been freshly repaved. For most of its length, it's a wide, smooth asphalt track. Two or three short sections are currently under repair, but otherwise there's nary a bump the whole way. The trail crosses several creeks and marshes spanned by wooden causeways -- more appropriate than steel or concrete. mIt seems that a good deal of thought went into the layout of the trail. The way it winds its way around trees suggests that as many as possible were spared during its construction.

Starting at Memorial Bridge and working south, some of the numerous sights along this path are Arlington Cemetery, Columbia Island Marina, Lady Bird Johnson Park, and one of the most interesting examples of public sculpture, the Navy-Marine Memorial. Past that is National Airport, where the planes take off and land scant yards from the bikeway, separated only by a small inlet. Most impressive.

The Washington Sailing Marina is a short ways south of the airport on the Potomac. About two miles south of the marina, the trail enters Alexandria and passes through parts of the waterfront, Old Town and right past the Torpedo Factory. The trail here, on city streets, is marked by well-placed green-and-white signs.

Beyond Alexandria the trail becomes quiet again, passing through stands of trees, meadows and Dyke Marsh. Through the marsh it's on one of the wooden causeways, offering one of its more interesting vistas. Then it moves through more open woods for several miles and crosses the parkway at Alexandria Avenue.

From here to Mount Vernon the trail assumes a rolling quality from small rises.At Fort Hunt Road the trail again crosses the parkway. Around this point is a scenic overlook toward Fort Washington, across the Potomac on the Maryland shore. Beyond that, the trail dips toward the river and follows the bank through several grassy picnic areas before heading into the woods for the approach to Mount Vernon. The quiet and shaded atmosphere make this short section one of the best parts of the whole trail.

Right before the entrance to the Mount Vernon parking lot is the trail's only real hill. It's not very long at all, but it is very steep and hidden by turns until it jumps out and grabs riders by their sprockets. Most riders probably will not be able to change gears swiftly enough to handle this hill with any ease.

Mount Vernon has restrooms, a snack bar and bike racks for public use. Water fountains and comfort stations are situated every few miles along the length of the trail.

This bike path is generally not so crowded as others, but still care must be taken, especially with regard to some of the blind turns.

The C&O Canal, brainchild of George Washington and object of William O. Douglas' conservation efforts, is a time machine that takes you back a hundred years or more, to when Cumberland was on the edge of the wilderness, and the Union and Confederacy battled at Antietam.

The Canal is one of the most popular parks in the area for almost any type of recreation: Stretching 184 miles from Georgetown to Cumberland, it presents cyclists with endless opportunities, and the daring among them with a considerable challenge.

The towpath is a packed-dirt-and-stone tarck up to 12 feet wide. Although in recent years it has eroded greatly from storms and flooding, by and large it's in good repair.

There are 35 Hiker-Biker overnight camping sites between Seneca and Cumberland, each with water, privy and fireplace. Situated every five to ten miles, and free, they help make the towpath suitable for trips ranging from several hours to a week or more.

In addition to the campsites, there are hostels at Seneca, Sandy Hook and North Branch; for information, check with the Potomac Area Council of the American Youth Hostels.

The going on the towpath is frequently slower than it would be on other bike paths, because the surface is rough, with tree roots sticking up.Toward the more popular (and populous) parts, such as Seneca, Great Falls and Georgetown, you'll have to share the path with a fair number of people -- no problem, really, but use care.

The Canal is endlessly fascinating, passing such places as Great Falls, Widewater, the Paw Paw Tunnel. The names of the towns along its route are also intriguing: Carderock, Point of Rocks, Sharpsburg, Little Orleans and Pigmans Ferry.

The setting is distinctively rural, with fields and forests flanking the canal at many points. The flora is outstanding three out of four seasons a year, and the fauna in the less-used areas is abundant, with squirrels, chimpmunks, raccoons, possums and birds dominating. You may see deer tracks or even a deer itself.

Of course, all along the canal are the locks, lock-keeper houses and other relics of the canal's heyday. The C&O Canal is a National Park, run by the National Park Service. All in all, it's a most pleasant place to spend any length of time cycling.