Pen y Bryn is a two-storey manor house, in Abergwyngregyn, Gwynedd, in north-west Wales, adjacent to the A55, five miles east of Bangor and eight miles west of Conwy. It is constructed mainly of broken stone, with roughly dressed quoins and a slate roof. The house is situated within Garth Celyn, a double bank and ditch, overlooking the Menai Strait to Anglesey. A smaller house was immediately adjacent in 1811 when Sir Richard Colt-Hoare recorded it; this was demolished by 1815. The present structure incorporates a four-storey stone tower. The present roof timbers were dated by dendrochronology to 1624, when the house was refurbished. There is evidence of long use with multiple rebuildings before 1624, but there is disagreement on the duration and nature of its mediaeval use. Construction history In 1303–06 building works at "Aber" were carried out on a large scale, including the importation of broken stone and of lime for mortar. The remains of the other candidate for such work, the high-status early mediaeval site, on and near the mound known as the Mŵd, do not now have masonry of broken stone and may not have been large enough to justify the quantities of material recorded. In 1553 Rhys Thomas and his wife Jane acquired the house from the Crown. The present roof timbers were felled between 1619 and 1624. The tower may be a slightly later addition, and there were further additions in the early eighteenth and nineteenth centuries. Garth Celyn The modern Garth Celyn is defined by the Royal Commission on the Ancient and Historical Monuments of Wales (RCAHMW) as a series of features, including the house Pen y Bryn itself, a large 'barn', and earthen terraces and scarps, collectively interpreted as an enclosure 90–100 metres across. The name "Garth Celyn" may be translated as "Holly Enclosure" or "Holly Hill" in Welsh. The use of the term "Aber Garthcelyn" has changed through time; as late as 1725, it could refer to the entire parish. Modern Garth Celyn has designated a scheduled monument by Cadw due to being 'a site of national importance'. An excavation was undertaken in 1993 by the Gwynedd Archaeological Trust. The complex included other structures, including a barn or gatehouse (possibly rebuilt about 1700 on earlier stonework) and the present tower. Claims that the early mediaeval royal palace was located on this site The Garth Celyn Trust exists to "protect and preserve