As the famous strait widens below the bridges the shores are tamer, and we come to the famous Caernarvon Castle, the scene of many stirring military events, as it held the key to the valleys of Snowdon, and behind it towers that famous peak, the highest mountain in Britain, whose summit rises to a height of 3590 feet. This great castle also commanded the south-western entrance to the strait, and near it the rapid little Sciont River flows into the sea. The ancient Britons had a fort here, and afterwards it was a Roman fortified camp, which gradually developed into the city of Segontium. The British name, from which the present one comes, was Caer-yn-Arvon--"the castle opposite to Mona." Segontium had the honor of being the birthplace of the Emperor Constantine, and many Roman remains still exist there. It was in 1284, however, that Edward I. began building the present castle, and it took thirty-nine years to complete. The castle plan is an irregular oval, with one side overlooking the strait. At the end nearest the sea, where the works come to a blunt point, is the famous Eagle Tower, which has eagles sculptured on the battlements. There are twelve towers altogether, and these, with the light-and dark-hued stone in the walls, give the castle a massive yet graceful aspect as it stands on the low ground at the mouth of the Sciont. Externally, the castle is in good preservation, but the inner buildings are partly destroyed, as is also the Queen's Gate, where Queen Eleanor is said to have entered before the first English Prince of Wales was born. A corridor, with loopholes contrived in the thickness of the walls, runs entirely around the castle, and from this archers could fight an approaching enemy. This great fortress has been called the "boast of North Wales" from its size and excellent position. It was last used for defence during the Civil Wars, having been a military stronghold for nearly four centuries. Although Charles II. issued a warrant for its demolition, this was to a great extent disregarded. Prynne, the sturdy Puritan, was confined here in Charles I.'s time, and the first English Prince of Wales, afterwards the unfortunate Edward II., is said to have been born in a little dark room, only twelve by eight feet, in the Eagle Tower: when seventeen years of age the prince received the homage of the Welsh barons at Chester. The town of Caernarvon, notwithstanding its famous history and the possession of the greatest ruin in Wales, now derives its chief satisfaction from the lucrative but prosaic occupation of trading in slates. [Illustration: CONWAY CASTLE, FROM THE ROAD TO LLANRWST.]