Ruins in Grounds of Abbey Hotel

The ruins comprise a large mediaeval building, traditionally identified as St Deiniol's Chapel, along with the remains of a smaller, likely later, structure attached to the west side. The main building, featuring an undercroft, is approximately 6 meters by 4.8 meters and slightly irregular in shape. It has high gables at both the east and west ends. Internal corbels on the north and south walls suggest a former division of the space into two bays, similar to those found at Lamphey. Marks on the gable walls indicate the presence of a former ceiling at collar-beam level. Original small, splayed square openings are high in each gable. An east window with a pointed head, other window openings, and two pointed doorways are present, although these were likely altered in the 19th century.

The undercroft is now vaulted in brick, but evidence suggests an earlier stone vault occupied the same position. A fragment of earlier masonry at the southwest corner belonged to a structure that may have later been rebuilt as a cottage. Corbels exist at a high level on the west gable of the main building, indicating a former lean-to roof. The apparent cottage has an open fireplace with a cylindrical-shaft chimney, potentially a whimsical 19th-century garden feature as it lacks an oven. A lean-to latrine is attached to the north side of the main building, and marks suggest the presence of a larger structure previously in that location.

In the mid-19th century, the owner, Miss Robson, altered the buildings to create a fernery. This involved rebuilding the undercroft in brick, installing heating flues, adding a stone staircase at the west end of the main building, glazing and altering windows, and constructing a low glass roof to avoid visibility from the surrounding garden. A slate water tank is situated at a high level, and a circular, brick-lined depression in the floor was probably a fishpond.

The ruins are listed for their substantial mediaeval origins and for the additional horticultural interest of their later 19th-century conversion to a fernery.