Ruins, name probably taken from the castellated shapes of the rocks nearby.

Dywedir iddo gael ei godi o dan gyfraith undydd unnos rhyw dri chant wyth deg o flynyddoedd yn ôl [1556] gan Robert wyn Griffiths a'i feibion ynghŷd a thrigolion Cwm Nantcol. Tŷ lled fychan ydoedd gyda chegin a siambr a chroglofft, un corn, ffenestri bychain, muriau trwchus, mortar pridd yn y waliau gyda llechi ar y to o'r ffridd islaw, sef Ffridd y Llyn, Derw oedd y sparas a'i dustiau. Torrwyd yr holl goed i adeiladu'r tŷ o'r tir o amgylch y lle. 

Adeiladodd Elis Jones dŷ arall yn Cystyllan, un mwy na'r un gwreiddiol gyda dau gorn a dwy ffenestr lloft. Tyddyn bychan ydoedd gyda thua 3 acer o dir a buarth a beudy. Ei ferch, Margaret Jones symunodd i Llam Maria i magu ei phlant. [Detholiad o 'Rhai o atgofion y diweddar Evan Jones 1936].

Erbyn 1908 roedd yn rhan o ystad Gors y Gedol ond yn ôl y Degwm rhoedd o'n gafael yn ei hun.

Yn Llais Ardudwy, rhifyn 39, 1978 cofiodd y Parch L.G Roberts mai 3 tŷ oedd yno o'r enw 'Gwyn Fryniau, Carleg Llwyd a Chastelll y Llan'.

'Clywais ddywedyd mai disgynyddion un o ffyliaid (court jesters) yr hen fychaniaid Gorsygedol oeddynt. ac fod y lle sef cystyllan ac ychydig dir i'w ganlyn wedi roddi yn etifedd iddynt gan deulu Gorsygedol' [erthygl yn archifdy Dolgellau Z/M/551/3]

Amryw o straeon am Dafydd Styllan, neu Dafydd y Gwn, oedd yn byw yna. Atgofion amdano a'i dywediadau ffraeth a bachog ar gael ar ddogfen ar wahan.

[Translated] - it is said that it was build under the undydd unnos (one day and one night) law around three hundred and eighty years ago [1556] by Robert Wyn Griffiths and sons along with neighbours in Cam Nantcol. A narrow house with a 'cegin' a chamber and crogloft, one chimney, small windows, thick walls, daub mortar in the walls with a slate roof from the nearby ffridd, Ffridd y Llyn, the beams and ceiling. The wood that was used to build the house was all cut from the surrounding land.

Elis Jones built the second house at Cystyllan, a larger one that the original with two chimneys and two 1st floor windows. It was a small 'tyddyn' with around 3 acers a yard and barn. His daughter Margaret Jones moved to Llam Maria, also a ruin, to rais her children. [translated extract from 'Rhai o atgofion diweddar Evan Jones 1963' (Memories from the late Evan Jones 1963)]'

By 1908 is was part of the Gors y Gedol Estate but the Tithe shows it was an isolated holding in 1840s.

[Translated] 'They say that they were descendants from one of the court jesters, the old Fychaniaid Gorsygedol. And that cystyllan and a bit of land was given to them as inheritance from the Gorsygedol Family'. [unpublished article in Dolgellau Archives Z/M/551/3]

in Llais Ardudwy, no 39, 1978 there was a contribution made by Rev. L.G. Roberts who remembers there were three homes there named Gwyn Fryniau, Carleg Llwyd and Castell y Llan'.

There are a few stories about Dafydd Styllan, or Dafydd y Gwn, who lived here. Recollections of him and his sharp wit are available on a separate document.

Cyfeiriad: Prosiect Treftadaeth Harlech ac Ardudwy. ‘Murddunnod Coll’, 2024.