From the Wikipedia page 
Woolwich Common is an area of military land located to the south of the town centre of Woolwich in South East London.
It is bounded on the south side by the A207 Shooter's Hill Road, and on the east by Academy Road (part of the A205 South Circular road) that the former Royal Military Academy fronts. Situated to the west is the Queen Elizabeth Hospital. The attractive Rotunda building on Green Hill to the north used to hold many artillery pieces now displayed at Firepower. The octagonal building, designed by John Nash, began life as a display space in St. James's Park during the peace celebrations there in 1814 and was re-erected in Woolwich between 1819 and 1822.
It is still possible to see soldiers from the nearby Royal Artillery Barracks (situated at the northern edge of the Common) training there occasionally. Formerly, the common was used extensively by the Royal Artillery as a training area, as the common is also close to the former gun foundries in the Royal Arsenal, Woolwich.