St-y-Nyll

St-y-Nyll is a large country house built in the neo-Georgian style. The walls are made of narrow brick, primarily in Flemish bond, with some ashlar dressings. It features a low-pitched hipped slate roof with narrow brick stacks positioned behind a parapet that has ashlar coping topped with cone or orb finials. The windows are large 12-pane sashes set in exposed moulded frames, complete with rubbed brick voussoirs and shallow stone sills. There is a platband cornice with openings for a parapet gutter below, and a plinth.

The garden front has a seven-window range, with a tall central stone doorway on the ground floor. This doorway is framed with an architrave and a segmental arched pediment supported by consoles, leading to a glazed door. The door opens onto two semicircular steps that descend to a wide terrace. The terrace is bordered by low walls made of rubble and rock-faced stone, featuring flat ashlar coping and steps leading to the lawns, which are flanked by stone piers topped with tall urns. To the right, there is a blind bay on the side elevation that has an added conservatory.

At the rear, the entrance elevation has a bay that steps forward at the center right, featuring a classical stone portico with a triglyph frieze, Doric columns, and an open pediment. The portico has a panelled stone soffit and double doors that incorporate a boar's head motif in relief. This doorway is flanked by narrow 8-pane sashes leading to the hall, and above it is a large sash window for the staircase. The left side has a four-window range, while the right side has two windows, with a single window at the first floor right.

The interior is believed to retain its original layout, with the rear entrance and staircase hall connecting through pillars to the central garden hall. The reception rooms, which face the garden, are thought to have original fireplaces in various styles, including Georgian, Adam, and 17th century. The rooms also feature moulded plaster cornices and polished wood or parquet floors.