Many consider Tongwynlais as the entrance to the South Wales Valleys from Cardiff, with its famous landmark, Castell Coch, on a hillside. The main route to the Valleys, and beyond to Mid Wales, the A470, runs alongside the village. To the north of the village is Fforest Fawr, a forest of about run by the Natural Resources Wales. Tongwynlais is separated from the rest of Cardiff by the M4 and the A470 to the south and west and hills and forestry to the east. Tongwynlais is considered to be part of the Cardiff North Rural Area.