At a distance of about 75 feet from the outer edge of the mound, and at a height of 14 or 15 feet above the level of the stone ring, is the entrance to the crypt. The threshold stone is 10 feet long by about 18 inches thick, and is richly ornamented by double spirals of a most elaborate and elegant character;[247] and at a short distance above it is seen a fragment of a string-course, even more elaborately ornamented with a pattern more like modern architecture than anything else on these mounds. The passage into the central chamber is, for about 40 feet, 6 feet high, by 3 feet in width, though both these dimensions have been considerably diminished, the first by the accumulation of earth on the floor, the second by the mass of the mound pressing in the side walls of the passage, so that it is with difficulty that any one can crawl through. Advancing inwards, the roof, which is formed of very large slabs of stone, rapidly becomes higher; and at a distance of 70 feet from the entrance, rises into a conical dome 20 feet in height, formed of large masses of stone laid horizontally. The crypt extends still 20 feet beyond the centre of the dome; and on the east and west sides are two other recesses, that in the east being considerably deeper than the one opposite to it. In each of these recesses stands a shallow stone basin of oval form 3 feet by 3 feet 6 or 7 inches across, and 6 to 9 inches deep. They seem to form an indispensable part of these Irish sepulchres, though what their use was has not yet been ascertained.