ONE OF the nice things about Washington is that a river runs through it. Have you noticed? The easy meander of the Potomac that forms Washington's southeastern frontier is one of the great uncounted blessings of life in the District -- the outdoors equivalent of the free museums.

It's not that people don't admire this comely stretch of urban river as they zoom across the 14th Street Bridge or fly along the center channel on their approachto National Airport. But it's surprising how few people ever move beyond looking at the Potomac to getting on it. Now that the Clean Water Act has strained out most of the effluvium that once turned the Potomac into a river of shame, Washington boasts some of the most enjoyable, convenient in-town paddling in the country. The city-bound sections of the Charles or the Hudson have nothing on us.

"People are always surprised by this part of the Potomac," says Judy Lathrop of Atlantic Kayak in Alexandria. "I've paddled in San Francisco and Seattle where conditions are often pretty harsh. This is a much more forgiving urban environment. And there's a lot more wildlife than you would expect."

This spring -- in search of paddling that features more time in my boat than in my car -- I've been rediscovering the waters of the Potomac within D.C. proper. Along the dozen miles of river between Chain Bridge and Woodrow Wilson Bridge lies a surprising gallery of marsh, parks and wildlife refuges. I do this whole run when I have half a day to spare and can arrange for someone to pick me up at Jones Point Park below Wilson Bridge. But there's a shorter option. For a little outing before work or before happy hour, the river between Georgetown and Alexandria boasts a world-class concentration of bridges, colossal statuary, stone sea walls and other marvels of civil engineering. I call it the Monument Mile.

If you work in or around downtown, the Georgetown-to-Alexandria reach is a waterborne workout 10 minutes away. I often launch at Thompson's Boat Center, the Park Service dock just below the Georgetown waterfront. It's $2 to put in here, plus a handful of quarters to park in the lot just off Rock Creek Parkway. This is the base of the Potomac's active rowing scene, and you may mix wakes here with crews of fours or eights being hectored along by their coxswains.

It's also a place to rent a canoe or a rowing shell if you don't have a boat of your own. I pull away from Thompson's in my sea kayak on a recent Saturday morning. The hours just after dawn are spectacular, the Potomac is empty except for a few hard-core aerobic rowers huffing laps up and down the river. I make my more leisurely way upstream a few hundred yards to the shadow of the Key Bridge, which marks the upper line of the truly urban section of the Potomac. The sea wall here forms the bragging wall for local crews -- neat middle-class graffiti covers every inch, extolling the supremacy of Georgetown Crew or Whitman Rowing.

At Key Bridge, I cross to the Virginia bank and turn downriver, ready for some steady paddling with the faint crawl of current. One of the nice things about this wide stretch of the Potomac is its reliable lethargy. Here at the upper reaches of the Chesapeake's tidal influence, the currents are rarely beyond the comfort level of even novice paddlers. Only a few miles upriver -- where the white-water boats play -- the Potomac is capricious and sometimes devious. Here it is languid and obliging.

About an eighth of a mile below the bridge, Roosevelt Island squats in mid-river like a fat goose. I take the channel to the left -- known as Little River -- and thread between the island and Virginia. The island -- an old plantation gone feral -- is thickly wooded. A great blue heron stands stiff-legged and staring just off the bank. On the southern tip, where I-66 hopscotches off the island on its way across the river, you can turn inland for a short detour through interior channels crowded with duckweed and fallen branches. Pulling south, the river broadens to a wide band running through downtown. Looking toward Virginia, the shoulder of the George Washington Memorial Parkway is grassy and tree-lined enough to approximate parkland, especially on a rush-hour-free weekend morning. The hallowed rises of Arlington National Cemetery come slowly into view as I near the Potomac's finest span, Memorial Bridge.

This water bug perspective on grand structures is one of the payoffs of paddling kayaks and canoes on the Potomac. Down here among the massive footings, the Great Seals of the United States that flank each arch loom like moons. And not until I saw them from the water did I notice that the keystones on the downriver side are decorated with abstract buffalo heads flanked by 10-foot-tall tomahawks. The bridge skips in low arches across to the Lincoln Memorial. The Rock Creek Parkway tunnel near the Kennedy Center spits out cars, which speed along the top of a limestone sea wall toward the head of the bridge and the muscle-bound golden horsemen that guard it. Behind them, the Watergate complex rises like a stack of film reels. Below the bridge, after you pass the parade of tour buses queued along the Mall, great floodgates strain the flow in and out of the Tidal Basin beneath the Jefferson Memorial. They strain me out too; there's no access to the Tidal Pool.

On the Virginia side, I duck into the lagoon at Columbia Island Marina. The boundary channel running alongside the Pentagon is a good place to look at pricey boats, and the gas dock attendant will let you pull out on his pier, giving you access to the marina snack bar for a mid-paddle breakfast. Refreshed, I paddle strong under a cluster of unremarkable bridges -- the concrete-and-steel, utilitarian spans that carry 14th Street, I-395, Metrorail and Amtrak across the river.

It's transportation central here. I wait under the railway bridge for a train, which shakes the surface of the water when it comes. And at that moment, a US Airways jet takes off from National a half-mile away in a near vertical, full-throttle arch that shivers the river even more. I love this unique access to a major airfield and paddle downriver to take up station at the very tip of the North-South runway at Gravelly Point. The wind is from the north, so the jets are taking off my way. Floating here, I have to lean all the way back in my boat to track the progress of the big planes as they thunder just a few dozen yards over head. After a few departures, my ears ringing, I paddle carefully up Roaches Run, through the culvert under the G.W. Parkway to the expansive waterfowl sanctuary behind. Wood ducks are here, in the lee of the airport and with a view of Crystal City, and they seem content with their noisy city setting. Directly across the river from National -- at the confluence of the Anacostia and the Potomac -- is Haines Point and the mouth of the Washington Channel.

If you have energy for an interesting detour, paddle up the channel, past the spooky sculpture of the emerging head on your left and manicured Fort McNair on your right. Soon you're among the working docks of the fish market on Maine Avenue. Further up the channel are the lower gates of the Tidal Basin, again locked to your entrance. Back on the river, I pull down the length of the National runway to Alexandria. It's a long paddle to Old Town, but worth it for the nice face this old harbor presents to the Potomac. If you're ready for a break or lunch, take out at the city docks near the Chart House restaurant. There's a snack bar at the docks or, of course, all of Old Town beyond. This is the usually the midpoint of my in-town Potomac outings, and I turn back upriver toward Georgetown and home. Occasionally, I can rope a friend or my wife into picking me up further downriver to return me and my boat to the car. Otherwise, there's no easy way to work a shuttle on the river and you've got to be ready to paddle back the way you came. From Georgetown to Alexandria and back adds up to an hour and a half to two hours of steady paddling. Doing it in the morning means I can be out of the water and at work by 10. Doing it in the evening means I take out right as sunset beckons me a few steps over to the Georgetown waterfront and a chance to replace those burned calories with an overpriced cocktail -- and a chance to toast anew my local river.

ON THE WATER

You can get started by renting a kayak or canoe at these outfitters:

ATLANTIC CANOE AND KAYAK -- 1201 North Royal St., Alexandria. Offers an extensive line of kayaking classes and kayaking tours throughout the entire Potomac and Chesapeake Bay region. Atlantic offers sunset and full moon tours of the Georgetown waterfront, Pohick Bay, Alexandria's Dyke Marsh and Piscataway Creek in Maryland (call for prices). 703/838-9072 or 800/297-0066. Web site: www.atlantickayak.com.

JACK'S BOATS -- 3500 K St. NW. Directly underneath Key Bridge, not far from the upscale Georgetown waterfront, the decidedly rustic docks of Jack's Boats can be found. Jack's rents sit-on-top kayaks (and canoes) for impromptu expeditions along the Georgetown waterfront ($8 for one hour, $15 for two hours, $20 for three and $25 all day). 202/337-9642.

THOMPSON BOAT CENTER -- Rock Creek Parkway and Virginia Avenue NW. Rents kayaks ($8 for a single per hour, $24 all day; $10 for a double, $30 all day), and you can launch your own craft from its ramp ($2). 202/333-9543.