In the southern side is a circular gate tower of Gothic shape. Here also are the portcullis grooves visible and a recess for the windlass, as well as the remains of arches over the moat, and a barbican beyond. A moat or ditch surrounded the fortress, on the two sides not washed by the Boyne, which was supplied with water by a small stream. Where the town wall joined the castle at the south-west angle a mound of earth has been artificially raised to the height of the castle wall. This was probably done for the mounting of cannon when the castle was re-fortified in 1647. One of the towers near this mound was cleared in 1836. It is of three storeys, and the upper part was found to be a pigeon-house, having holes for 60 or 80 pair, while the lower storey contained a postern leading to the level of the moat water. In 1425 it is recorded that the King granted the custody of the dove-cot to Thomas Brown, with pasture called the Castle Orchard. The north angle of the bawn contains the ruins of several buildings, one being of three storeys with a high gable, and four large windows in the wall towards the river. The piers for the arched roof are still to be seen, and it is likely to have been the banqueting hall or chapel. A large vault extends under part of it. In one of the towers near this the mint is supposed to have been situated. Another tower contains the remains of a small chapel. The keep consists of a rectangular figure, on each side of which a small square tower abuts, thus forming a twenty-sided figure from which missiles could be showered in all directions. The walls of the centre tower are twelve feet thick, while those of the adjoining ones measure from four to six feet. Winding stairways lead to the summit, at some 60 feet from the ground, while on each angle of the centre tower is a square turret nearly 17 feet in height. After Hugh de Lacy had been granted Meath in 1173 he erected the castle of Trim to guard his possessions. He surrounded it with a moat, and furnished it with stores. He then entrusted its custody to Hugh Tyrrell and proceeded to England. No sooner had he left than Roderick O’Connor, King of Connaught, descended on Trim with a large army. Tyrrell sent messages to Strongbow for aid, but in the meantime, finding himself unable to hold the fortress, he evacuated and burnt it. [Illustration: TRIM CASTLE.] The news was brought to Strongbow as he marched to its relief, and upon his arrival finding the Irish had retreated, and having nowhere to lodge, he pursued them and killed a hundred and fifty. Giraldus states that the castle was rebuilt by Raymond le Gros, who had marched to its relief with Strongbow, having joined the expedition on the day of his marriage. King John stayed at Trim, but he did not lodge in the castle, although one of the towers is called after him, and his signet ring is said to have been found in the enclosure.