When we sent amateur photographer Greg Ercolano the top photo of the Los Angeles River and asked him to shoot the same place today, it took him a few hours to find it. "I'm about 90 percent sure it was the right place," he says of the spot in the northeast corner of Griffith Park. "But today there's a freeway in the course of the original river, and obviously there are no landmarks to compare." To tame the flood-prone river in the 1930s and '40s, the Army Corps of Engineers mixed and poured some 3.5 million barrels of cement along its course, and these days, the river is usually little more than a fetid trickle in a concrete channel as wide as a highway. Nonetheless, groups such as Friends of the Los Angeles River refuse to give up on it and are trying to restore the riparian habitat.