 The Rhondda also has the remains of two Medieval castles . The older is Castell Nos which is located at the head of the Rhondda Fach overlooking Maerdy . The only recorded evidence of Castle Nos is a mention by John Leland who stated that " Castelle Nose is but a high stony creg in the top of an hille " . The castle comprises a scarp and ditch forming a raised platform and on the north face is a ruined drystone building . Due to its location and form it does not appear to be of Norman design and is therefore thought to have been built by the Welsh as a border defence ; and must therefore date before 1247 when Richard de Clare seized Glynrhondda . The second castle is Ynysygrug , located close to what is now Tonypandy town centre . Little remains of this motte @-@ and @-@ bailey earthwork defence as much was destroyed when Tonypandy railway station was built in the 19th century . Ynysygrug is dated around the 12th century or early 13th century and has been misidentified by several historians , notably Owen Morgan in his book ' History of Pontypridd and Rhondda Valleys ' who recorded it as a druidic sacred mound and Iolo Morgannwg who erroneously believed it to be the burial mound of king Rhys ap Tewdwr . 
