The distance from Fourteen Locks at Rogerstone in Newport to Brecon is about 43 miles so the whole journey could be done at a leisurely pace in seven separate walks and in its total would provide a whole variety of country explored. Anyone who has read the books of Alexander Cordell will have a good grounding in the history of the southern half. Although he didn't specifically write about the northern half his book, The Song of the Earth, was set on the Neath Canal and that will provide you with a picture of a working canal as a sharp contrast to the leisure use that canals have today.
This is a really beautiful seat, I do hope that it doesn't get spoiled by carvings and graffiti.