Four Seasons is heading for downtown Manhattan. It will retain its midtown location but will also occupy the first 22 floors of an 80-story residential tower that is planned near Ground Zero. The plans form part of a proposal from World Trade Center developer Larry Silverstein. The new tower will be Robert A.M. Stern Architects with an anticipated opening by 2011. The hotel will have 175 rooms, a restaurant, pool, spa and health club with several suites, including one 3,700-square-foot royal suite.