In the year 1814, when the Allied Sovereigns visited London, a tent-like building was erected in Carlton House Gardens on the north side of St. James's Park, wherein the Prince Regent entertained his royal guests. The structure of this building is, I believe, of interest to architects, as it embodies structural details which, although common to-day in factories and exhibition buildings, were considered to be somewhat of a tour de force in the early nineteenth century. The building is circular, 116 ft. in diameter, enclosing about 10,600 sq. ft, the roof being composed of girder ribs meeting in the centre and resting on brick walls. It was originally covered with thin boarding and painted canvas, but in recent years the roof has been covered with lead and a central supporting pillar has been added. In 1819 the Rotunda was removed, by the order of the Prince Regent, to Woolwich Common, near the Royal Artillery barracks, to serve as a model room, or store, for examples of artillery. A small contemporary model of this building is exhibited in the London Museum.