The Arroyo Seco (Spanish for "dry creek") is a stream in Los Angeles County, California. It is a major tributary to the Los Angeles River. The stream begins near Mount Wilson in the San Gabriel Mountains, and flows into a reservoir created by the Devil's Gate Dam. After flowing away from the reservoir, the stream flows in a concrete channel through La Cañada Flintridge on the west and Altadena on the east; then through Pasadena, South Pasadena, and the neighborhoods of Highland Park and Montecito Heights in Los Angeles before flowing into the Los Angeles River at Elysian Park. Its watershed covers 46.7 square miles (121 square kilometers). 