Penllergare provided inspiration for the expression of Dillwyn-Llewellyn's talents. Taking in the adjacent estate of Nydfwch and based on the work of his father, Lewis Weston Dillwyn, John exploited the natural beauty of the site in his grand design to create a landscape planted with a rich variety of trees, shrubs and exotic plants. He erected one of the first purpose-built orchid houses in the kitchen gardens, from 1836, an observatory, around 1851-2, was built close to the mansion house, and experiments with an electrically powered boat (built before 1848 by John himself) were conducted on the Lower Lake.