Barbican House Museum is owned and operated by the Sussex Archaeological Society. The building has been a museum since the early twentieth century and houses the Society's archaeology and fine art collections. There are permanent galleries, a temporary exhibition gallery and an audio-visual presentation on the history of Lewes from the prehistoric period through to the mid-twentieth century. The museum also has a significant photographic collection recording both East and West Sussex from the mid-nineteenth century.
As well as the public galleries, the building is home to the Society's library. This is an exceptional resource and collection. Material covers archaeology and local history and it also includes working papers from some of the county's most noted historians and archaeologists.