Orleans House Gallery is one of the better free art galleries in outer London, housed in a remarkable early 18th-century building that includes the Grade I-listed Octagon Room — a spectacular baroque pavilion added around 1720, with plasterwork attributed to Giovanni Bagutti. The gallery holds the Richmond Borough Art Collection, covering the history and art of the Thames Valley from the 17th century to the present.
The Octagon Room alone is worth the visit: a perfect small baroque interior, with coved ceilings, gilded plasterwork, and a sense of intimate grandeur quite different from the more monumental baroque interiors of central London. The gallery runs a programme of temporary exhibitions alongside the permanent collection. Entry is free; the gallery is a short walk along the river from Marble Hill.