What is this?

Manchester is an amazing city!  Although its not my "birth town" it is now my "home town" and one I am very proud to be a part of...  I saw this today - just outside my Manchester office - I must have walked by it / over it hundreds if not thousands of times before and never, ever noticed it! (being a blipper really does open your eyes doesn't it..).  Does anyone know what it is, what it symbolises?  My youngest daughter knew immediately and you can find out more here...

Well done Manchester - you are an example to us all.

P.s Anyone notice my shiny shoes :)