The longest way from Connecticut Avenue to Reno Road is by Melvin Hazen Trail. It is less than half a mile, maybe the shortest hiking trail in the city, but you'd better pack a lunch. If your heart is in the right place, it should take an afternoon.

"There are a lot of secret places in here," says Jonathan Weiner, a veteran, 9-year-old explorer of this wooded finger of Rock Creek Park that is severed from the rest of the park by Connecticut Avenue and surrounded by one of the richest residential neighborhoods in the city. "Follow me and I'll show you where the monster Smog lives."

We'll meet Smog, look for buried treasure and find out who Melvin Hazen is later. First we have to get you to this wooded place where the air is cool, a stream gurgles and birds spend their days stealing each other's worms. It may not be the Appalachian Trail, but then you can't get there by subway.

The sign appears to be a joke. Three blocks north of the Cleveland Park Metro stop on the west side of Connecticut Avenue, it sits between a podiatrist's office and an apartment building, advertising a hiking trail. What you see is a paved driveway leading into a parking lot.

But walk past the three green trash dumpsters, beyond the signs that promise violators will be prosecuted, and you come to a curtain of green. Enter and the day changes. In summer the foliage is thick enough to hide all but a few brick specks of the surrounding neighborhood. The sound of traffic becomes a distant hum. Shade and sun occupy, then lose ground as the wind blows the canopy of trees.

"This is a very precious place," says Hope Babcock, an attorney for the National Audubon Society who hikes, jogs and walks her dogs on the trail. "There is such a variety of terrain, so much wildlife . . . I don't know who Melvin Hazen is, but God bless him."

Hazen was the District of Columbia's surveyor for 20 years at the beginning of this century. In the 1930s he became president of the District's Board of Commissioners. Ten years later the National Park Service bought the land to protect the stream that carries water from the high country of Wisconsin Avenue to Rock Creek. They named that tributary after Melvin Hazen.

Hazen died and the woodland grew. By the mid-1970s, the trail that had been blazed by the Park Service was almost completely overgrown. One man who had hiked it in its prime, Carl Jones, joined forces with the Potomac Appalachian Trail Club in 1977 and began clearing the trail again.

In 1978 after hundreds of hours of volunteer work, the trail was officially reopened. Now there are rough-cut log steps at the steepest part and a wooden platform across the soggiest. But because of its location, the trail is still unknown to all but a few hikers.

"I don't think I've ever seen more than one other person on this trail at a time," says John Healy, another lawyer who lives in the neighborhood and walks the trail on his way to buy groceries on Wisconsin Avenue. "This way I mix business with pleasure."

While adults keep out of the park or on the trail, neighborhood kids have staked out all the woods as their own. They have given names to worthy places, like Queen Pits and the Rat Hole. They have converted a tangle of fallen oak trees into a fort that they alternately attack and defend with stick swords. And they have conjured up a monster named Smog to get them running when the summer days are slow.

"Hey Smog, come on out Smog," says Jonathan Weiner, bravely putting his head into the dark opening of a giant drain pipe at one end of the trail. This day he is introducing another 9-year-old, Benjamin Sassaman, who just moved into the neighborhood from Pennsylvania, to the lore and legend of the park.

"John, who is a teen-ager, once got a blowup swimming pool and paddled it up the pipe," said Jonathan to his new friend. "At least he says he did. Frankly, I'm not so sure."

The two boys walk along a tree trunk that has fallen across the stream. Rocks are thrown. Treasure is hunted. Somewhere along the banks of the stream, there is said to be buried gold doubloons and pieces of eight. Jonathan has had no luck in his digging. But he is patient. With summer approaching, there will be time he says to find almost anything in his dense playground.

"I try to come down here in my spare time," Jonathan says.