I'm assuming anglers go both sides.
I've used Pontsticill and Dolygaer reservoirs for trail running. Lovely views when you go up on the trails surrounding both reservoirs. Also a decent walk/trot to Talybont reservoir if I'm feeling particularly fit.
All on the doorstep butt.
Gets a bad press Merthyr by some but where else could you see beautiful nature and then score heroin within 5 minutes.
Something for everyone.
They should use that as a tourist slogan.