PHOENIX— The first new hotel to be built downtown since 1976, a 1,000-room Sheraton, has its official ribbon-cutting today. The 31-story building is the largest hotel in Arizona. It is located a block from the Phoenix Convention Center and contains 80,000-square feet of meeting space. Starwood Hotels & Resorts Worldwide, parent of the Sheraton brand, estimated the cost of the new hotel to be $350 million.