Plas Berw comprises a ruined medieval hall house and a mansion of 1615 (NPRN 15801), set on two sides of a forecourt or garden. It probably had walled gardens and was situated within a deer park (NPRN 265407). Notices of the site pre-date the existing buildings and the park may have earlier medieval origins, although there does not appear to have been an earlier house on the site.

The late medieval house, dated to about 1480, was probably built for Ithel ap Howel, one of the descendants of the twelfth century lord of Menai, Llywarch ap Bran. It is a single north-west to south-east range. Opposed doorways led into the passage at the lower end of the hall beyond which was a two storey solar. A service or kitchen block lay below the passage to the north-west. The area of the later court on the north-east was paved. An upper floor was inserted in the hall in about 1536 and a small three storey wing or tower was added to the solar block in the late sixteenth century.

Sources: RCAHM Anglesey Inventory (1937), 100-102
Longley in Archaeologia Cambrensis 140 for 1990 (1991), 102-119
NMR Site file
CADW Listed Buildings Database (5500, 5501)
Haslam, Orbach and Voelcker (2009), The Buildings of Wales: Gwynedd. Pevsner Architectural Guide, page 213.

RCAHMW, October 2009.