MY FRIEND Mark lives in one of those well-appointed new apartment complexes that have sprung up like weeds around MCI Center. His building has everything, including a fitness center and a spacious, two-level roof deck with gas grills and a swimming pool. It's one of those situations where you find yourself fishing for cookout invites:

"Hey, man, we should get everyone together one of these days and fire up the grill."

Still, as I'm enjoying the last rays of the setting sun at Afterlight, the Friday night happy hour on the roof of the Hilton Washington Embassy Row Hotel (2015 Massachusetts Ave. NW; 202-265-1600), my jealousy diminishes. This isn't my house or my roof, but it's the kind of pool party I'd like to throw.

The expansive Hilton sundeck has everything you need: multiple bar stations; a pool surrounded by patio lounge chairs; a cook working a large grill; plenty of large, round tables shaded by umbrellas; a killer sound system; and a dance floor covered by a large tent. (For other area rooftop destinations, see Page 28.)

DJs Double o7 and Shawn Greene handle the music, spinning soulful house and hip-hop to keep the vibe funky. "This is what we call Afterlight," Double o7 announces. "It's Friday. It's time to untuck your shirts."

The lively, diverse crowd is a mix of women in sundresses and tank tops as well as business suits, guys wearing casual-Friday khakis and those who've stopped off to trade their ties for sport shirts and designer sunglasses.

The lounge chairs by the pool are filled with folks working on their tans or just decompressing after a long week. The rectangular pool is not big enough for laps -- it's only five feet deep and better suited for a refreshing dip or dangling your feet -- but being near the sparkling water has a soothing quality.

A steady stream of cheeseburgers and chicken breast sandwiches is coming off the grill and come with all the toppings and a bag of gourmet chips. Everyone around my table is sipping a beer or a margarita (frozen or on the rocks); both are $4 all night long.

Many people are gathered around the edges of the building, taking in the sweeping panoramas that reach from the National Cathedral through Georgetown, past the high-rises of Rosslyn and Ballston, across the Potomac River to the Washington Monument, St. Matthew's Cathedral and the canopy of trees that blankets Dupont Circle. It's a chance to see the city in a whole new way.

Most people don't come for the view though -- they come here because the combination of sun, water, DJs and food and drink specials makes this the best outdoor happy hour in the city.

Afterlight debuted at this location in 2002 as a party called Twilight. Promoters Shawn Broxson and Matthew Brady had built up their weekly house music gig at Adams Morgan's Rendezvous Cafe and were looking for a new summertime challenge.

"We wanted to do something outdoors," Broxson says. "Brady had been to a wedding reception over [at the Hilton rooftop] and thought it was a cool place. We basically cold-called them, went over there and pitched the idea to them. It was love at first sight."

Twilight was a smash, bringing house music DJs and fans together for drinks and dancing in a perfect setting. But then one neighborhood resident complained about the noise from the late-night party and threatened to sue the hotel if it didn't kill the event. Just like that, Twilight went dark.

The Hilton finally worked out an agreement with the neighborhood more than a year later, promising to keep the volume down and end parties earlier. But it was too late to salvage the 2003 season, and there was a bigger blow later that summer when Brady died in a motorcycle accident.

Structural problems kept the roof closed through 2004, but Broxson, flush with memories of Twilight, was still planning a comeback. He kept in touch with Hilton general manager Gary Lashley and launched Afterlight on Memorial Day weekend.

"We've had to take the edge off, getting the noise levels down," Broxson explains. "I know Shawn [Greene] doesn't want to hear me say this, but we're taking the focus off the music and concentrating more on the party."

Because of the hotel's agreement with the community, Afterlight (www.afterlightdc.com) functions more as a happy hour and early evening gathering place than a wild nightspot. Doors open at 5 and the music stops by 11, although that message hasn't quite gotten out.

"Three years ago, I think people understood that it's an early party," Broxson says. "[Afterlight] starts right after work, and the music starts at 5:30. If you want to change, you can do that at the hotel," he laughs. "Bring your flip-flops. But now we still have people showing up at 9, 10, 11 o'clock. . . . This is [set up] so people can come here and then go out somewhere else afterwards, or they can go home."

It's not an expensive night out, either. Admission is always $5; draft beers and margaritas are $4; and everything that comes off the grill is $5.

Afterlight has been improving incrementally each week -- the grill was added after partygoers complained that they had to leave to get a bite to eat; a second bar area arrived after people had to wait too long for drinks; the hotel brought up a frozen-drink machine after patrons asked for frozen margaritas and summer cocktails.

All Broxson asks for is consistency. "We want to be a place where you can come every week and hear the same style of music and feel the same vibe," he says. "I like that neighborhood bar feel. This is a neighborhood bar, but on a rooftop with a great sunset and a pool."

Once Afterlight began drawing weekly crowds, the Hilton decided to take advantage of the setting by adding additional events and promoters, each with their own flavor. It's worth noting that these events are weather-dependent, and it's best to check the forecast (and the organizer's Web site) before heading out.

Every Thursday, the Hilton's roof is taken over by Euronet International, a networking group that organizes events for a mix of European ex-pats, World Bank staffers and party-loving Americans.

Previous events have included galas at the Embassy of Finland, happy hours at downtown lounges, sailing lessons and bike trips. Founder Aki Partanen says he wants to shake things up a bit, so the European Happy Hour will be different every time. One week features salsa dance lessons and a DJ playing Latin dance favorites, the next brings Scandinavian and Russian pop music.

Thursday, Partanen has planned a "Brazilian Luau" with samba lessons and discounted drinks.

A schedule is posted on the group's Web site (Euronetinternational.com), and the site also allows guests to RSVP and save a few bucks on admission ($10 if you RSVP through the site; $13 at the door). Like Afterlight, it's a happy hour affair -- doors open at 6:30, and the party lasts until 10.

The latest addition to the hotel's lineup is Sunday Heights, an afternoon pool party that seems like an excellent way to wrap up the weekend. "In the past, I've done a lot of nightclubs," explains organizer Alan Salgado. "I promoted events at Platinum and Dream. But my crowd is the older nightclub crowd -- they're over 25 and are more apt to go to happy hours and special events. Some are what I call the 'ex-club crowd.' They used to go out a lot, but now they have degrees and they're working and they're not into standing in line or being pushed around by bouncers."

His solution is a leisurely Sunday afternoon, lounging around post-brunch with food and mixed drinks while DJ Moh spins a mix of Latin, house and hip-hop. Here's the clincher: Unlike the Thursday and Friday events, the $10 cover charge at Sunday Heights includes access to the pool. Guests bring their bathing suits, and the hotel supplies towels, showers and locker rooms. (Again, save a few bucks by getting on the guest list at www.sundayheights.com.) Sunday Heights began two weeks ago, and while it's a little early to judge, it was fairly slow last Sunday, despite the gorgeous weather.

The pool saw more use from hotel guests and families than from the people who came out to enjoy a cocktail and lie out in a bathing suit.

But Salgado is confident the event will do well. "If you live in an apartment in D.C. or you have a house with roommates, you really don't have anywhere [like this] to go," he says.

It's a pool party for the rest of us, and we don't even have to worry about cleaning up afterward.

Afterlight, the Friday happy hour on the Hilton Washington Embassy Row Hotel's roof, draws a relaxed crowd. Patrons can get cheeseburgers hot off the grill and $4 beers and margaritas all night long.Doors to Afterlight open at 5, and DJs such as Shawn Greene keep the funky beats going until 11.