The map covering this area is Ordnance Survey Explorer 166 "Rhondda & Merthyr Tydfil", 1:25,000 scale.
For a rewarding walk, start out from the Visitor Centre. Parking coordinates are provided below. If you walk along the wall surrounding the Tyla-du Plantation, be sure to notice the interesting boundary stones placed along it.
Alternatively, for a shorter walk, there is a primitive road leading up onto the common. Access is between Pontlottyn and Fochriw, and alternative parking coordinates are suggested below.
The final approach to the cache is quite steep, and, on a clear day, you will be rewarded with commanding views across the Rhymney Valley to Mynydd Bedwellte. Look north, and you may just see Pen y Fan, Corn Du, and the tip of Cribyn. Spectacular! You may even enjoy the company of paragliders overhead, as I did when placing this cache.
Please wear sensible footwear with good grip, as the grass near the cache location can be very slippery, whether wet or dry, and the exposed dirt and rocks can be somewhat unstable. The cache approach is not recommended for small children -- please leave them supervised at the top of the hill.
I hope you enjoy this stunning location. Happy hunting!