You are standing on a traffic island, a refuge for pedestrians. It's on the south west side of Canterbury. Behind you is the Wincheap Roundabout which the merging of traffic from Wincheap (leading away behind you) and the city inner ring road.
The line of the city walls passes just in front of you and just inside that line is the Norman Castle (turn left for a better view).
The street ahead is unsurprisingly known as Castle Street. It's a pleasant short walk from here into the centre of the city heading towards the Cathedral.