Ascending to the fourth floor, there are two large rooms separated by the cross-wall, the arcade of which was probably filled in with wooden partitions. The larger or western room is known as the "Council Chamber," and the other as the "Royal Apartments." Neither has any fireplace. Over the vaulting of the chapel, close under the flat, lead roof, there is a curious cell about seven feet high, lighted by small loop windows, which extends the entire length of the chapel. Formerly used as a prison, it must have subjected its miserable inmates to even more trying variations of heat and cold than the famous "_Piombi_" of Venice. With the exception of the chapel, its crypt, and sub-crypt, which were vaulted throughout, all the floors were originally of wood, and were supported on double rows of stout oak posts, which in their turn sustained the massive oak main floor beams. The forebuilding, on the south face of the keep, was probably added by Henry II. It survived until 1666, as it is shown in a view of the Tower executed by Hollar about that date; but it appears to have been removed prior to 1681. The chapel of St. John is a fine example of early Norman ecclesiastical architecture. It consists of a nave, with vaulted aisles, having an apsidal eastern termination. It is covered by a plain barrel vault, and on the fourth floor level has a triforial gallery, also vaulted. It is connected by two doors with the gallery in the thickness of the wall that surrounds this floor, from one of the windows of which it is said that Bishop Ralph Flambard effected his remarkable escape. It is probable that at first (except the chapel, which was covered by its own independent roof) there were two separate high-pitched roofs, one covering each division, and not rising above the battlements, the wall gallery serving as a kind of additional fighting deck, for which reason it was carried round the triforium of the chapel. As the need for this diminished, two large additional rooms were gained by raising the central wall a story, and superposing a flat, lead roof. The absence of privacy, fireplaces, and sanitary accommodation on this fourth floor, with the cold draughts from the stairways and windows of the wall-gallery, must have been well-nigh intolerable; nor could wooden screens, hangings, or charcoal brasiers have rendered it endurable. It is not surprising, therefore, that under Henry III. the palace was considerably enlarged, or that these chambers were abandoned by him for warmer quarters below, in the Lanthorn Tower "k," and its new turret "J" although the chapel and council chamber continued to be used down to a much later date.