The indoor-outdoor plaza of Rockefeller Group’s 1221 Sixth Ave. is poised to undergo the most sweeping transformation since the former McGraw-Hill tower between West 48th and 49th streets opened in 1969.

A redesign by Italian architects Citterio-Viel & Partners, to cost in the “mid-to-high eight digits,” will replace the space-wasting sunken plaza with a new, public-friendly plaza at sidewalk level.