Large dungeons are situated below the keep, and there are many bricked-up passages and secret chambers. One of the former is said to lead to a neighbouring rath. The guard-room on the south-east side is hewn out of the rock. Numerous bones have been found in different parts of the building. The site of the castle was evidently chosen to guard the river ford and the pass of the Slieve Bloom Mountains into Tipperary. Many bones have been found in a field near the river. A village once surrounded the castle, but only the ruins of the houses now remain. The O’Carrolls, whose chief stronghold the castle was, are supposed to have wrested it from its original builders, the Danes. In 1154 Henry II. granted Ely O’Carroll to Theobald de Walter, but he was entirely unable to take possession of any but the lower portion of the kingdom. In 1489 John O’Carroll died of plague at Leap. The visitation was at this time so bad that hundreds of bodies lay unburied. Gerald Fitz-Gerald, 8th Earl of Kildare and Lord Deputy of Ireland, set out for Leamyvannan in 1513 to put down a rising of the O’Carrolls. He failed to take the castle, “as was seldom the case with him,” and retreated to collect fresh forces. Returning with a splendid company he was shot by an O’More while watering his horse at the River Greese, near Kilkea, and he died a few days later at Kildare. Three years afterwards his son attacked Leap, and took the stronghold, of which it is recorded, “there was scarcely any castle at that period better fortified and defended than this, until it was demolished upon its warders.” In 1522 the Earl of Kildare made it a charge against his rival, Sir Piers Butler, Lord Deputy, that he had lent O’Carroll cannon to defend Leap against him in 1516. The charge was hardly denied, but the defence was put forward that the attack on O’Carroll was unwarranted. Mulrony O’Carroll died at Leap in 1532. It is recorded that he was “a triumphant traverser of tribes; a jocund and majestic Munster champion, a precious stone, a carbuncle gem, the anvil of the solidity, and the golden pillar of the Elyans.” He was succeeded in the chieftainship by his son, Ferganainm, but the succession was disputed by a senior branch of the family who were in possession of Birr. Ferganainm enlisted the aid of his father-in-law, the Earl of Kildare, who received a wound during the dispute which hurried his end. It was, no doubt, at this time that a terrible massacre took place at Leap Castle upon the rival branch of the sept, who had been invited to the stronghold under the guise of friendship. Lord Deputy Grey may have had this act of treachery in his mind when writing of O’Carroll, Baron of Ely, in Edward VI.’s reign, he speaks of him as “false.” It is stated that this O’Carroll made submission to Lord Leonard Grey in 1537.