The setting of the novel and the film is The Olchon, a real valley in the Welsh borders.
The stable lad who accompanies the old farmer's wife to the horse show really is Victor Krum from Harry Potter. The map that is hidden is based on the Hereford Cathedral Mappa Mundi 1350. Of course they would not have been able to hide it up a hillside without the whole valley knowing.
Both Iwan Rheon and Tom Wlaschiha were in Game of Thrones (2011). Rheon as Ramsey Bolton and Wlaschiha as Jaqen H'gar.