The Equatorial Observatory, Penllergare

The Equatorial Observatory in Penllergare is a Grade II* listed building that serves as both an observatory and a laboratory. The observatory features a cylindrical tower made of tolled squared stone, topped with a 20th-century metal-clad cylinder. This windowless tower has small square recesses near the base and an ogee cornice that shows signs of erosion and has been patched with cement.

The laboratory is a single-storey structure built in a neo-Jacobean style using yellow patent blocks, which are larger than standard bricks. It has a slate roof that is hidden behind a parapet. The stone plinth supports terracotta-block walls, and the parapet features a central neo-Jacobean gable that was rebuilt in imitation blocks in 1981. There is one window on the north side, which has a 20th-century cross-window that may have been placed in a former door opening. The window surround is chamfered with terracotta block voussoirs. The south side has a similar window to the right and a central door, both with matching chamfered surrounds and voussoirs, featuring 20th-century door and window fittings.

The interior of the observatory is not accessible, while the laboratory consists of a single room with terracotta block walls and a fireplace located on the right end wall.