This is Springfield Flour Mill.  In a recent presentation by an expert Augustinians learned that this mill was a monster.  As big as they come.  You can see Hilderthorpe Road in the background. It appears on 1890 maps but was probably demolished soon after.

By studying maps we can deduce that the track that runs through the gateway is now where Springfield Avenue lies and the mill is about midway down on the west side.  This means the foundations of the Mill must be under where the recently demolished houses once stood about half way down.

Keep a look out for the foundations as this now open space is developed.