ON THE OUTSKIRTS of Washington, 45-foot walls rise from the river to protect the sort of fort Rambo would have loved -- not the electronic, high-tech type with radar everywhere, but the kind they used to defend with monster guns firing giant black cannonballs.

This fantasy fortress is a great place to take kids with a rat-a-tat-tat mentality; here's a place you can go with the militaristic flow while tucking a little history into their weapon- crazed brains. If you plan it right, you can tuck in a little fishing or picnicking as well.

The place is Fort Washington, this city's oldest river fort, planned as the first line of defense before the War of 1812. The British, unfortunately, didn't see it that way -- they sent a land force around to Washington by way of the Patuxent River during that war, burning the infant city in 1814 within full view of the fort.

The fort commander found himself squeezed between a British-occupied Washington and a British sea force coming up the Potomac. So unnerved was he by this dillemma that, at the first sign of British ships, he blew up the magazine and deserted the fort -- an act for which he was later court-martialed.

No trace of that fort remains today. Pierre L'Enfant, who planned the Capital City (blame him for those circles), was asked to design the present fort. However, he was fired within a year when it was discovered that the government project wasn't moving but large chunks of money were. The compromise layout, which was eventually completed in 1824, contained the latest in fort design -- not one, but two tiers of guns aimed at the river.

First stop outside this fort is the yellow Visitors Center, once home to the commanding officer. Here, a slide show, displays and a bookstore should get you oriented.

My kids don't suffer slide shows gladly, so we poured instead through the main gate of the fort and peeped into the guard room and cramped, damp cells built into that wall.

"The cells were used mainly for sleeping by prisoners who spent their day doing the camp dirty work," says Park Ranger Jeff Descheemaeker. "Like scrubbing the latrines. They were real fussy about keeping those clean," he says.

Just past the gate to the left are buildings that served as officers' quarters and barracks. Between the two runs a long, cool tunnel leading to an empty room where four guns could be placed to protect the fort's back wall. A wire gate closes off the rest of the area -- which served as an eight-hole privy.

Down toward the river side there are green doors to what look like stables. "Those are the casemates for that second tier of guns," Descheemaeker explains. In peacetime -- a condition that covers most of the fort's history -- many of the guns moved out of these casemates (rooms where the cannon were mounted for firing through narrow slits) and the company laundress moved in.

"They passed a rule in the early 1800s saying that the laundress must be married to someone at the fort," Descheemaeker explains, "because they found that if it was a single woman with 40 or 50 guys around, there would be fights." Married enlisted men weren't allowed in the Army during peacetime in the 1800s, but marrying the laundress was a way to get around the rule.

The doors are closed to these casemates, but the cannons on the upper tier, with their semi-circular runners for the carriages, are easily explored. The riverfront wall affords what has to be one of Washington's most spectacular river views. On a clear day you can see all the way to the Washington Cathedral.

It wasn't the view that interested the kids ("blam! blam!"), but the nearly three-ton Barbette cannon, which sends off 24-pound shot. This is mounted on a carriage so visitors can see (but not move) how it was aimed. It takes a five-man, experienced crew only two minutes to prepare and shoot. "But you couldn't do more than a couple of rounds that fast -- it wears out the crew," says Descheemaeker.

Most Sundays throughout the day, Descheemaeker and his friends shoot off a few lesser rounds from the 12-pounder model 1841 howitzer nearby. Of course, that doesn't begin to equal the number of imaginary rounds shot off by the younger visitors.

The fort you see today has never heard a shot fired in anger; this is the 19th-century version of deterrent defense, Descheemaeker says. At the start of the Civil War, Ft. Washington was the only deterrent outside Washington, though by war's end a circle of 67 forts ringed the city.

But in those first precarious days, the fort was occupied by one lone ordnance officer, described by Union Gen. Winfield Scott to the London Times as an "old Irish pensioner"; and the fort could probably be had, he thought, "for a bottle of whiskey."

Not so, says Descheemaeker. "There is nothing on the ordnance officer's record to indicate a drinking problem, or anything but outstanding conduct," he says. "And he was probably Scottish, anyway." It was this officer who sounded the alarm to Washington officials, asking that the fort be garrisoned immediately at the start of the war.

Between 100 and 300 troops were stationed here throughout the conflict, "and it was considered good duty," Descheemaeker says. "Nobody was shooting at you, the rations were good and the work was hard but not too onerous."

But the men were not allowed to go more than a mile away during their half-day off, he says -- a fact that restricted their fun and probably contributed to the liquor problem. "It was always a problem," Descheemaeker admits, "especially during the war, when you had bootleggers making bad alcohol."

Liquor led to a number of fights and occasional deaths in the fort, Descheemaeker says, but overall health was generally good -- "It's conspicuous by the absence of records. There was a case or two of typhoid or malaria, but no real outbreaks."

The garrisons left after the Civil War, and the fort basically shut down until the 1890s, when Congress decided to build or expand a series of "seacoast" forts, including Ft. Washington. Remnants of that expansion are some ugly concrete batteries outside and below the fort where guns were hidden; and towers where they were controlled.

The fort was garrisoned off and on during the World Wars -- the brick houses standing on grounds outside the fort were quarters and PX for those men. But in 1950, the place was finally turned over to the Department of the Interior, which maintains its grounds today.

The park contains picnic grills, fields for ball games and a few choice spots along the river for fishing. "They're starting to catch bass in there," Descheemaeker says.

And on one of these shining autumn weekends, it's a great place to brng a soccer ball, a Frisbee, a package of hot dogs and a kid with a penchant for fantasy.

TO THE FORT

From the Capital Beltway, take Indian Head Highway (Route 210) south four miles to Fort Washington Road. Turn right, and follow the road to the fort.