They strolled down 16th Street NW, four teenagers with cameras and three adults, in the suffocating humidity.

Bob Caputo, 56, a National Geographic photographer, stopped abruptly at a neatly maintained tan-brick apartment complex, noticeable only because of its height. "Guys, your assignment is to get on top of this building," he said. "In my job, I probably spend maybe 5 percent of my time taking pictures. The rest I spend getting into position."

The young people, some of the 14 teens from District schools taking part in National Geographic's third annual photo camp, looked toward the roof with trepidation. For most of the summer, they intern at the organization's headquarters, but they spend four days exploring one Zip code in the city -- this year, it's Mount Pleasant -- with the guidance of a photographer in a project modeled after the ZipUSA feature that runs monthly in National Geographic.

But getting onto a roof? This was photography?

The teenagers entered the foyer and buzzed the manager. No answer. A passing resident let them in, and they headed for the rental office. No one was there.

Momentarily defeated, they went back outside and scanned nearby buildings for another vantage. Just as they began to head elsewhere, a woman in floral pants walked up. The manager. "Do you want to see an apartment?" she asked.

Charlene Valeri, 56, who works in National Geographic's digital imaging lab, explained that they were more interested in the roof.

The woman listened, nodded and took them in an elevator to the 10th floor, then up two flights of stairs, then through three doors that she unlocked. William Boney Jr., 16, from McKinley Technology High School, hummed Beethoven's Ninth for dramatic ambience. He had never tried photography but said the camp had interested him in taking some classes.

Finally, the roof. To the southeast, the Washington Monument and the Capitol dome were white silhouettes against the hazy sky. To the west, houses dissolved into the verdure of Rock Creek Park and the Gothic spires of Washington National Cathedral jutted into view. Over the east edge of the roof, 16th Street sprawled before them.

"You take the picture, you take the moment, and that will never be there again," Walter Daniels, 15, a McKinley student, said as he snapped photos with a digital camera.

"There's this mix of things that are forgotten, that you're just letting crumble, things that they're trying to restore and things they're trying to build over," said Hillary Edwards, 17, a student at Duke Ellington School of the Arts.

Meanwhile, Lauren Grimes, 16, from Benjamin Banneker Academic High School, took pictures of the row houses, finding beauty in the faded paint and chipped facades. She saw things in Mount Pleasant that made it stand out, she said: the yellow-orange mangos being sold by street vendors, the Latino mothers with their children, the stores offering Italian and Central American foods.

This is how students should think about photography, Caputo said. The purpose of photo camp, he explained, is not to build technical prowess but to develop the ability to look at the world -- and to think of it as a story.

The photographic stories of Mount Pleasant, the teenagers knew, will go into a final presentation of their work, and the best photos might be displayed in a cafe. They also will be exhibited in the National Geographic building with photos from the four other cities where the camp is held, said Kirsten Elstner, director of VisionWorkshops, a nonprofit mentoring group contracted by National Geographic to run the program.

When they thought they had shot their fill, Caputo had another question.

"Is this the best time to be here?"

They realized what he meant. The light would be better at sunset. After the building buzzer, the resident, the manager, the elevator, two flights of stairs, three doors and a half-hour of meticulous photography, their work had just begun.

From the roof of an apartment building, William Boney Jr., 16, gets an intimate view of Mount Pleasant. Boney is in National Geographic's photo camp.