Not within the city limits of Cardiff but just a short (19 minute) train ride north. This is one of the UK's great medieval castles.
The interior of this church has been painted as it would probably have looked in 1520.
If visiting Cardiff, please note that three other castles are within a few miles of this castle. For St.Fagans Castle & The National History Museum of Wales - leave Cardiff Castle - turn right and walk down street for 5 minutes to bus stop outside Holiday Inn. Use service 32 or 320 for the 20 minute journey. For Caerphilly Castle, turn left on leaving Cardiff Castle - walk along Queen Street for 14 minutes to Queen Street station. Trains to Caerphilly are at 15 minutes intervals (except Sundays when less) and the journey takes 15 minutes. To see photos of these other castles plus Castell Coch - click the Cardiff tag.
Just a short bus ride (32 / 320)from Cardiff city centre (first village once you leave the city). Free entry to this Castle dating from mid 1500's plus the extensive grounds & museum buildings. From M4 J33 take A4232 for about 1 mile and follow brown signs to car park - beware of sharp turn off the sliproad from the expressway.
Not within the Cardiff boundary, but at M4 J28 near Newport.
Located between Swansea & the Brecon Beacons National Park.