Castell Gronw (Gronw Castle)

castell gronw castle gronw blodeuwedd mabinogion castell gronw castle gronw blodeuwedd mabinogion

Within the grounds of Pen Y Bont Farmhouse by Bala Lake (Llyn Tegid) in Snowdonia, lies the listed ancient monument of Castell Gronw (Gronw Castle).  

Castell Gronw is a scheduled ancient monument with CADW (the Welsh Government’s historic environment service). The Royal Commission on the Ancient and Historical Monuments of Wales lists Castell Gronw as a medieval castle which dates back to approx 1202. 

It has been linked to Gronw Pebyr of Penllyn and as such is shrouded in the mysterious ancient folklore of the tales of the Mabinogion.  Learn about the tale of Blodeuwedd the flower maiden, as told in the fourth of the Four Branches of the Mabinogion, here.


Whilst nothing remains of the original 800 year old castle structure, the "Motte" or mound is roughly 20-23m in diameter and some 4.5m high, with a level summit about 9.0m across. There is a curving boundary ditch to the south-west which is thought to represent a bailey enclosure roughly 25-35m deep. From the top of the Motte there are fine views over the North end of Bala Lake, also across to the charming town of Bala and of the surrounding countryside.


Castell Gronw is in private ownership, however the owner allows access to members of the public each year on the 1st March (St David's Day).    Guests to the neighbouring Pen Y Bont Farmhouse have private access at all times.


Please note that the Castle mound is a protected ancient monument and must in no way be damaged; in particular, English and Welsh Law expressly prohibits the use of metal detectors on the site.




Link to Royal Commission on the Ancient and Historical Monuments of Wales Site - Castell Gronw listing


How Castell Gronw may have looked in 1202



Castell Gronw in Relation to Bala Town and Lake


Castell Gronw Location Plan


Castell Gronw Detailed Location Plan


Castell Gronw Reference Details

Name                                      Castell Gronw, Bala 

Historic County                        Merioneth 

Modern Authority                    Gwynedd 

Ordnance Survey Reference    SH930350

Eastings/Northings                  293000   335030

Type                                       Timber Castle (Motte)  

Remains                                  Earthwork 

Coflein Record                        303420

Historic Environment Record    3203

Scheduled Monument               Listed


Mysterious Owl Related Happenings around Castell Gronw  - read more here


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