The 'Great Pile' comprising the buildings surrounding Artificers Court and Basin Court were erected between 1717 and 1720, the buildings being used as storehouses and workshops. In 1764 a sundial was erected over the Main Entrance, and it is this building, now called Dial Square which survives. It was used as a turning and engraving shop, and guns cast in the Foundry would have been machined here.

It is typically Vanbrughian, and is certainly more likely that Vanbrugh was responsible for its design than Andrew Jelfe the Clerk of Works for the Ordnance at the time.