The Diamond St. is a street located in the city of San Francisco, California. It is known for its unique diamond-shaped street pattern, which was designed by architect and urban planner Daniel Burnham in the early 1900s. The street is also home to many businesses, including restaurants, shops, and galleries. The term DEL, which is a three letter acronym, stands for 'Downtown Express Line, ' which is a public transportation line that runs along The Diamond St.