We next turn our attention to the adjacent barbican tower, whose massive walls are seamed from top to base by huge, gaping rents, through which the daylight peers; yet so great is their tenacity they still remain intact, and support the original stone roof. Each story is pierced with loopholes, ingeniously constructed to prevent missiles entering from below. The spacious courtyard enclosed by the outer walls is carpeted with velvety turf, whereon 'the quality' are wont to foregather from far and near to wield the tennis-racket, and contest for 'deuce' and 'love' upon the selfsame spot where, in the brave days of old, the Harcourts and De Valances, and all the flower of Norman chivalry, flung down the gauntlet or broke a lance upon the field of honour, while fair spectators waved encouragement from every arch and balcony. Beside the great central keep a labyrinth of crumbling walls, towers and arches, mainly of Edwardian date, cluster together in 'most admired confusion.' Here are pointed out the remains of the chapel of St. Nicholas, given by Montgomery to the Norman abbey of Sayes. A chamber is usually pointed out, in the building called the Exchequer, as that in which Henry VII. first saw the light; but Mr. Cobb suggests a room in the tower overlooking Westgate Hill. Unfortunately, the arms and badges noticed by Leland no longer exist to mark the scene of that interesting event. Clambering down a flight of broken steps in an obscure corner of the North Hall, we enter the vast cavern known as the Wogan; a very curious and characteristic feature of Pembroke Castle. As we ramble over the damp and slippery floor, by such light as can struggle in through the huge sally-port and a narrow, pointed window, we find ourselves in a spacious, natural vault sunk deep in the living rock; its rugged walls and roof festooned with hartstongue fern, and stained by oozing moisture--a weird, fantastic spot, such as the shade of the primæval cave-dweller might frequent, should he elect to revisit the glimpses of the moon. Sheer from the 'main Rokke' upon which the castle is founded, rises the vast, circular keep or donjon tower, which formed the central stronghold of the fortress. This is undoubtedly one of the most ancient parts of the castle, having been erected by William Strongbow the elder, 'Rector Regis et Regni,' as he proudly styled himself; who was Earl Mareschal of Pembroke during the reigns of Richard Coeur-de-Lion and John.