Parish Church of St Mary

This is a simple church with a long, continuous nave and chancel, with a south chapel addition that is flush with the east end. The building is constructed of random rubble with a renewed slate roof. The walling incorporates a quantity of squared red sandstone blocks that are probably reused Roman material from the site.

The west end features rough-kneelered and stone-coped gable parapets with a large surmounting double-bellcote. This bellcote projects slightly beyond the line of the west wall and is carried downwards to rest on four rounded corbels. In the centre of this projection is a carved stone crucifix set in a shallow cusped, arched niche of 15th-century type. The bell openings are depressed-headed with triangular profiled rubble coping to a flat top and a central stone gablet. A deeply-recessed west door with a gently-pointed arch contains an 18th-century studded plank door.

The north side of the nave has three post-Reformation 3-light mullioned leaded windows. The windows to the left and right use reused sandstone and slate-stone respectively, while the centre window has 19th-century pale sandstone mullions. Wide, segmentally-arranged sandstone voussoirs appear between the first two windows from the left, testifying to an earlier opening. A simple 15th-century 3-light mullioned window with arched sandstone heads is set in the east end.

The south chapel is adjoined to the south and flush with the east end. It has a 2-light mullioned window to its east side with wide, cusped, arched heads, and a similar 3-light window to its gabled south face with original ironwork. Above, an eroded sandstone plaque formerly bearing the initials EW and GW flanking the Williams arms is inscribed with the date 1591. Two further post-Reformation windows are set in the nave's south wall: that towards the west has three lights with slate mullions, and that towards the east is a wooden 2-light window. Beyond, towards the west end, a 15th-century rubble south porch (largely rebuilt as a vestry in the 19th century, though retaining its west wall and roof structure) now has a small, arched and cusped window to its south face that was reset and probably originally in the porch's east wall.

The interior has a long, continuous nave and chancel with a simple arched-braced collar roof consisting of 31 clustered trusses, probably of the 14th or early 15th century. The floor is flagged. Late 19th-century figurative stained glass is set in the westernmost window of the north wall. A plain bowl font on a column, presumably of early Medieval date, stands in the nave. A round-arched niche to the left of the east window is a fragment of the pre-15th-century east wall. Furnishings date from around 1830 and include simple pews with moulded rails to flat bench ends. A sunk-panelled octagonal pulpit stands on a moulded base, and a stall with open Decorated tracery is present.

The south chapel opens out from the chancel, with a supporting bressummer for its wide, flat opening carried on a figurative engaged capital set into the east wall that is perhaps 13th-century and reset. The chapel has a 2-bay roof with arched-braced collar trusses with plain struts, protruding dowels, and chamfered decoration. Above the chapel's east window is a long oak board bearing the inscription in raised letters: "EDWARDVS : WILL: IAMES: AR: ET: / GRACEA: UXOREI: Q HOC: OPVS: FIERI/ FECERVNT: ANNO: DOMINI: 1591." This refers to Captain Edward Williams of Maes-y-Castell, High Sheriff of Caernarvonshire in 1570. The west wall of the chapel features a mural tablet with an arms cartouche to Hugh Davis of Caerhun, d.1721. The east wall bears a monument to Catherine Hester Hemming and family, d.1829. The vestry (former south porch) has a 2-bay 15th-century collar-truss roof with windbraces.