The Royal Engineers Museum, in the working Brompton Barracks complex, traces the history of the Corps of Royal Engineers from the Norman Conquest to recent operations in Afghanistan. The collection is enormous and idiosyncratic: pontoon bridges, signal lamps, captured enemy weapons, the only surviving section of the original Channel Tunnel boring machine, Gordon's Bible from Khartoum, and an entire gallery devoted to military diving equipment.
It is open Tuesday to Sunday and is one of the most rewarding small museums in the south-east. Allow at least two hours; serious enthusiasts can easily make a half-day of it. There is a good cafe and a substantial shop. Free parking on site. Access is via the public entrance on Prince Arthur Road — the rest of the barracks is restricted.