The Palm House or Orangery

The Palm House, also known as the Orangery, is a palm house built in 1871 by Sir Matthew Digby Wyatt, featuring terracotta relief by Blashfield. It is constructed from limestone ashlar, cast iron, and glass, showcasing an Italian style with a tripartite composition. The structure has 13 bays, with a central 3-bay pavilion that includes a tall glazed arcade supported by pilasters and round-headed arches with console keyblocks. Terracotta roundels are located in the spandrels of the central arch, and there is a moulded stone cornice and an "attic" adorned with a long terracotta relief of classical figures. At the top, an octagonal glazed dome is set within a balustraded parapet.

On either end of the central pavilion are one-bay pavilions that mirror the arcade design, complete with moulded cornices and balustraded parapets. These are linked by lower 4-bay wings featuring glazed bays separated by pilastered piers, a plain entablature, and a balustraded parapet. Inside, the central domed space is divided from the wings by 3-bay stone arcades that resemble the facade, and it contains a central pool. Similar arcades also separate the wings from the end pavilions. The wings are topped with a glazed triple-span roof supported by circular cast-iron columns. The Palm House is situated at the head of the central formal axis of the Italian Garden. Castle Ashby park and gardens are recognized in the Historic Buildings and Monuments Commission Register of Parks and Gardens for Northamptonshire at Grade I.