The Cairngorms consist of three large elevated plateaux adorned with low, rounded glacial mountains, and divided by the passes of the Lairig an Laoigh and the Lairig Ghru. The range gives the sense of being a single plateau, because the passes that cut through them are not very deep: the summit of Lairig an Laoigh lies at 740 m, whilst the summit of the Lairig Ghru is at 835 metres above sea level at the Pools of Dee, where the water may be frozen over even in mid-summer. This means a walker could cross between the Cairntoul (1293 m) – Braeriach (1296 m) massif to the Ben Macdui (1309 m) – Cairn Gorm (1245 m) massif and thence onto the Beinn a' Bhùird (1196 m) – Ben Avon (1171m) massif without descending below the 740m summit of the Lairig an Laoigh. The range is drained by the Rivers Dee and Spey; and the latter's two tributaries: the Rivers Feshie and Avon.