China Lake Naval Air Weapons Station is the Navy’s main air weapons test center, and is among the largest and most diversified military sites in the nation. It is divided into two distinct geographic areas, north and south, which together cover more than 1,700 square miles. The north part, where a few thousand people go to work daily, is where most of the research, development, testing, and evaluation takes place, and includes the main base, airfield, impact areas, propulsion test sites, laser ranges, supersonic test tracks, and many other facilities, such as Michelson Lab, Skytop, Area R, and radar test sites at Junction Ranch. The southern half of China Lake is used primarily for training, and includes electronic combat ranges with simulated sea and land targets. China Lake started out as the Naval Ordnance Test Station, a World War II rocket test site for Caltech, which was also used to develop detonators for the Manhattan Project.