Mowing concrete

Yes thats it, Im curious about this so this is for former occupants (you know who you are) & I want to know for how many years this patio & path at the back of number 2 has been mowed and called grass / lawn. Sue was just edging the path but didnt really find the edge... the only visible parts were the 2 dark circles in the slabs to the left bottom corner so I always assumed they were like stepping stones across the lawn... so this afternoon mainly a small job turned huge but the results were great. Auntie Silvia was out all the time so she may have a shock when she returns the pretend grass or carpet as we were refering to it as we pulled it up in sheets, has gone.