There were three routes from Brecon to Abergavenny in Gerald’s time, and for some unknown reason, the party took the most difficult.
The easiest route ran east of the Black Mountains, down the Rhiangoll and Usk valleys and past Tretower. Tretower’s castle and manor house are the best surviving medieval monument in the region today. There was also a route down the Vale of Ewyas via Llanthony Priory. The route they took was the most difficult of the Black Mountain passes, though an established route in the twelfth century. The route climbs over two thousand feet above Talgarth and drops down to the heavily-wooded ravine of the Grwyne Fawr stream.