The Serpentine Sackler, a new outpost of London’s Serpentine Gallery, will open on 28 September. It is five minutes’ walk from the main gallery, over the Serpentine bridge in Kensington Gardens. Built as a gunpowder store in 1805, the Neo-Classical building has been refurbished and extended by the architect Zaha Hadid, and will have a gallery space and a restaurant. Although the figures are not being officially disclosed, the cost of the project was around £15m, of which £5m was pledged by the Mortimer and Theresa Sackler Foundation. Other donors include the New York mayor and media owner Michael Bloomberg and the Carphone Warehouse tycoon David Ross. The first exhibition is on the Argentinian artist Adrián Villar Rojas (until 10 November).