Arllen-fawr (formerly Garthgelynen-fawr)

Arllen-fawr farmhouse, formerly known as Garthgelynen-fawr, is a two-storey building with a four-window facade facing south, away from the road. The exterior is finished in white-painted slate and features a slate roof that slightly overhangs the eaves, supported by brackets. The left side of the front has a symmetrical arrangement with three windows, a central door, and chimneys at both ends. A portion of a plat-band is visible to the right of the door. The windows are four-pane 19th-century horned-sash types, including an additional bay on the right. The front door is semi-glazed and set within a panelled casing, flanked by plain pilasters that support a projecting entablature with carved volute brackets. The entablature consists of two sections with large dentils and an ogee profile. The sides and rear of the building are made of unpainted, uncoursed slate, and the rear roof has a low pitch.

Inside, the entrance room features a late 18th-century relocated staircase on the right, characterized by thin turned balusters, turned newels, a cut string with bracketed and moulded stair ends. There is significant exposed timber framing throughout, with both decorative and utilitarian elements in the partitions and ceilings. The room to the left is likely the original parlour, divided by main beams into four sections, with large chamfers and flat-laid ceiling joists that are simply moulded at the edges. The rear of the house showcases much exposed lozenge-braced timber framing visible in both the front and rear rooms. In the front bedroom on the left, there is an eared 18th-century timber fireplace surround, featuring a plain frieze and beaded moulding at the top.