The maximum height of a building or other structure, including elevator or stair bulkheads, accessory water tanks or cooling towers, chimneys, parapets, arbors or trellises and flagpoles, located within the Special United Nations Development District, shall not exceed 550 feet above the established grade of the easterly side of Second Avenue midway between East 43rd and East 45th Streets. No portion of any building within the Special United Nations Development District may be built to a height greater than the present height of the United Nations Secretariat Building within 200 feet west of the westerly boundary of First Avenue. No portion of any development on the south side of 44th Street within the Special United Nations Development District may be built to a height greater than 183 feet above curb level or 15 stories, whichever is less. However, energy infrastructure equipment and accessory mechanical equipment shall be permitted obstructions above all such height limits, subject to the provisions of Section 33-42.