Family Search have an interactive map called "England and Wales Jurisdictions 1851" showing parish (and other) boundaries with optional background maps such as Ordnance Survey. There is also a Search facility, do read the guidance notes to get maximum benefit from this useful resource. See here for further background information to assist in the interpretation of this data
Various landscapes - on the People's Collection Wales site
You can see pictures of Llanwrthwl which are provided by:
You can see the
administrative areas in which Llanwrthwl has been placed at times in the past. Select one to see a link to a map of that particular area.
Victorian Powys for schools site - Map of Llanwrthwl in 1891 and in 1847.
Map of the parish of Llanwrthwl in the County of Brecon - on the People's Collection Wales site
You can see maps centred on OS grid reference SN911624 (Lat/Lon: 52.249253, -3.59725), Llanwrthwl which are provided by: