Correct Merthyr Imp! Your forum name suggests a proximity to the BMR.
What a cracking little railway. Unusual rolling stock and fantastic scenery.
It's actually a few years since I last visited it, but I think that photo was taken near Dolygaer at the point where the BMR deviates slightly from the original formation so as to avoid a sailing club or some such.
The fascination to me is seeing how it fits into the former Brecon & Merthyr infrastructure and viewing what remains of that and its connections, especially at the Pant end and at Pontsticill. E.g. this view of the old Pant station which I took about seven years ago.