in their excellent book , `` new york 1960 , architecture and urbanism between the second world war and the bicentennial , '' ( the monacelli press , 1995 ) , robert a. m. stern , thomas mellins and david fishman provide the following commentary relating to the project 's design by wallace harrison , who was very active in the design of the united nations complex : `` in 1963 harrison 's vision of towers at the north end of the u.n. site , dating back to his x city proposal of 1946 , was at last realized when ground was broken for the two towers that would become 860-870 united nations plaza ( 1966 ) .