The deal was simple: The city would let developers build tall at Cityfront Center, Chicago’s largest real estate development of the 1980s. In exchange, there would be beautiful buildings, streets, parks, plazas and a riverwalk. Yet the architecture, with rare exceptions, is mediocre. The public spaces were supposed to be vibrant and interconnected. Instead, they are unfinished, underachieving, largely disjointed and even, in one case, off-limits to the public.