Anyway took some digging but it was part of an old viaduct that got demolished but this part was left over. Here is a glimpse of it from street view.
Not as interesting as other stuff but very enlightening for me to find out about it as we never knew anything when we climbed it as kids, glad there is some interesting history behind it at least.
https://goo.gl/maps/BmLgrGjKMQK2



