Explore details about location Pen yr Allt. Pen yr Allt is a location situated within the Caerphilly alongside other areas such as Lon-y-twyn, St Asaph's Way, Crescent Road. Additionally, some smaller parts of Pen yr Allt include specific areas like Ffordd Traws Cwm, Heol Waun Fawr, Ffordd Erw adding to the diversity of its landscape.