I think that is the castle at the side of Rivington ressy, part of the Lord Leverhulme follies same as the Chinese gardens half way up the Pike.
If it is we used to get the bus to Horwich when we were kids and go and play ‘army’ firing metal staples(not paper staples-the bent nail type) at one another with elastic bands off your thumb and fore finger – by heck they didn’t half hurt when the hit.
Not been there for 40+ years
edit
can I add, at the side of Lower Rivington Reservoir.