This main site of the museum forms the gatehouse and annex of Guildford Castle, which the staff help to run.

In 1903 Fredrick H. Elsley was appointed joint Librarian and Curator of the Society's collection of books, manuscripts and artefacts.

Highlights include sceptre handles and religious headdresses’ from the Romano-British temple site at Wanborough, a large collection of Mesolithic handaxes from Farnham, and the full excavation assemblage from the Tudor site of Farnborough Hill Convent, which was published by the Museum under the title Pots and Potters in Tudor Hampshire.

In 1907 it accepted a donation from Gertrude Jekyll, the celebrated garden designer, of her entire collection of objects relating to "Old Surrey".

Highlights include a napkin featuring an embroidered portrait of Queen Elizabeth I (believed to have been used by her), fragments of a Zeppelin bomb dropped on the St Catherine’s area of Guildford in World War I, and a green velvet suit purchased in Carnaby Street, London, in the 1970s.

This building was enlarged in 1911, when an extension was built in the Castle Arch gardens to house the Gertrude Jekyll Old Surrey Life collection of artefacts which helped to inspire her lifetime collaborator architect Edwin Lutyens.

The Museum was again extended in 1927 when the Borough Council purchased 48 Quarry Street, a 19th-century town house, and offered to convert the building and land adjacent to it into a muniment room for the Archaeological Society's archival collections.

A previous exhibition, entitled "A Few of My Favourite Things", featured objects chosen by local people from the Museum's reserve collections.

Guest curators include Anne Milton MP, Bishop of Guildford Christopher Hill and High Sheriff of Surrey, Elizabeth Toulson.

Objects on display include a 400,000-year-old hand axe from Swanscombe in Kent, and a napkin used by Queen Elizabeth I which features her embroidered portrait and an image of St George slaying the Dragon.