In Subdistrict A-1, the underlying height and setback regulations set forth in Sections 43-43 (Maximum Height of Front Wall and Required Front Setbacks) and 43-44 (Alternate Front Setbacks) shall not apply. In lieu thereof, the following provisions shall apply:

1. Street wall location
   
   The street wall of any building shall be located on the street line and extend along the entire street frontage of the zoning lot up to at least the maximum base height specified in paragraph (b) of this Section. On the ground floor, recesses shall be permitted where required to provide access to the building, provided such recesses do not exceed three feet in depth as measured from the street line. In addition, the street wall location provision of this paragraph shall not apply along such street line occupied by a public plaza as set forth in Section 37-70 (PUBLIC PLAZAS).
2. Base height
   1. Along wide streets
      
      On wide streets, and on narrow streets within 50 feet of their intersection with a wide street, the street wall of a building shall rise without setback to a minimum base height of 125 feet and may rise to a maximum base height of 155 feet.
      
      However, where the height of an existing adjacent street wall fronting on the same street line rises to a height exceeding 155 feet before setback, the maximum base height may be increased to the height of such existing adjacent street wall but shall not exceed a base height of 205 feet. In addition, where existing adjacent street walls on both sides of the building rise to a height exceeding 155 feet before setback, the maximum base height of such building may be increased to the higher of the two existing adjacent street walls, except in no instance shall the base height of such building exceed 205 feet.
   2. Along narrow streets
      
      On narrow streets, beyond 50 feet of their intersection with a wide street, the street wall of a building shall rise without setback to a minimum base height of 85 feet and may rise to a maximum base height of 135 feet.
      
      As an alternative, the minimum and maximum base heights applicable to a wide street may be applied along a narrow street beyond 50 feet of a wide street, up to a maximum of 100 feet from such wide street.
3. Required setbacks
   1. Along wide streets
      
      For buildings, or portions thereof, located on wide streets and on narrow streets within 100 feet of a wide street, the portion of such building above the applicable maximum base height set forth in paragraph (b)(1) of this Section, shall be set back from the street wall of the building at least 10 feet along a wide street and at least 15 feet along a narrow street, except such dimensions may include the depth of any permitted recesses in the street wall. Above such required setback, any portion of a building on the zoning lot shall be considered a “tower.”
   2. Along narrow streets
      
      For buildings, or portions thereof, located on narrow streets beyond 100 feet of a wide street, the portion of such building above the applicable maximum base height set forth in paragraph (b)(2) of this Section shall be set back from the street wall of the building at least 15 feet along a narrow street, except such dimensions may include the depth of any permitted recesses in the street wall. Above such required setback, any portion of a building on the zoning lot shall be considered a “tower.”
4. Tower Regulations
   
   Each story of a tower above the required setback shall not exceed a maximum lot coverage of 40 percent of the lot area of a zoning lot or, for zoning lots of less than 20,000 square feet, the percent set forth in Section 43-451 (Towers on small lots).
5. Maximum building height
   
   No height limit shall apply to towers.