Built by John Dillwyn Llewelyn in 1851/52 and situated towards the side of (the now demolished) Penllergare House, the Observatory is one of the few remaining 19th century structures. It is a monument to the estate’s illustrious past and today is registered as a Scheduled Ancient Monument by Cadw.

The family were passionate amateur scientists (particularly in photography, astronomy and botany) and it was here c.1856 that John and his eldest daughter Thereza, took one of the first photographs of the moon.