In a helicopter above [New York City], Stephen Wiltshire of London looked down at the streets and sprawl. He flew for 20 minutes. Since then, working only from the memory of that sight, he has been sketching and drawing a mighty panorama of the city, rendering the city's 305 square miles along an arc of paper that is 19 feet long. He is working publicly in a gallery at the Pratt Institute in Brooklyn. I always memorize by helicopter," he said, pausing from detailing the corners of a street on the Brooklyn side of the Williamsburg Bridge. Mr. Wiltshire sees and draws. It is how he connects. Until age 5, he had never uttered a word. One day, his kindergarten class at a school for autistic children in London went on a field trip. When they came back, he spoke. "He said, 'Paper,' " his sister, Annette Wiltshire, said. "The teacher asked him to say it again. He said it. Then they asked him to say something else, and he said, 'Pen.' " With pen and paper in hand, he drew what he had seen that day. In time, a clever teacher taught him the alphabet by associating each letter with a place he had drawn - "a" for Albert Hall, "b" for Buckingham Palace, and so on. Now 35, he has already drawn eight major cities after flyovers. He has his own Web site and gallery. By unpacking in exquisite detail the riches that he absorbs in a glimpse, Mr. Wiltshire has built a bridge to the world that had once been cut off to him.