The tragic thing about Piccadilly Gardens is that they went down an incredibly ambitious route and got Tadao Ando to design it but then completely fucked his original ambition over.
Ando conceptualised it as a proper city centre park. The hated wall was supposed to filter out noise and the hustle and bustle. It was never supposed to have cafes and shops in it, and the materials used weren't to his spec, hence why it's now a litter and dirt infested shithole.
I read something in an architecture magazine years ago that said Ando and his team of architects were disgusted at what happened and basically disowned the project.
Manchester was handed the opportunity to have an amazing and ambitious public square designed by literally one of the top architects on the planet but decided to save a few quid, buy some cheaper concrete and whack in a Cafe Nero instead. The people responsible for that decision should be hung.