A brown sign with an arrow pointing diagonally up and left, and the following text.
Castell Coch; Castell Caerffili; Caerphilly Castle [Cadw symbol] Parc Treftadaeth; Rhondda ; Rhondda Heritage; Park [Industrial heritage symbol] .
The M4 doesn't have a junction 31 - the number was reserved for use north of Cardiff but no junction ever materialised there. Instead we jump straight to 32, which is one of the most important interchanges in South Wales and connects us to much of the Valleys, including these sights.