Complex sentence: Designed by Skidmore, Owings & Merrill, construction was completed in 1986, and the building is comprised of two towers: a 60-story Main Tower and an 11-story Auxiliary Tower.
Split into simpler sentences: Designed by Skidmore, Owings & Merrill, construction was completed in 1986. The building is two towers: a 60-story Main Tower and an 11-story Auxiliary Tower.