Penywern, built in 1839, was initially the main barracks for soldiers stationed to keep the peace in Merthyr Tydfil after the 1831 Merthyr Rising. It was owned by the Dowlais Iron Company which used the reservoirs and ponds to feed water to the Dowlais Works.
There is an upper and lower pond situated on either side of the A465 Heads of the Valleys road, west of the ASDA store. Anglers can find bream, roach, tench, perch, barbel and carp.