At one time the favourite route to the summit of either Dumyat or Castle Law was via the prominent gulley which runs almost straight up the southern scarp face, and continues down the gently sloping north face. This gulley was formed by the erosion of a fault, resulting from the juxtaposition of soft pyroclastic rocks on one side against harder andesite and basalt on the other. This has resulted in an area where hard andesite slightly overhangs, and is the darkest and least exposed part of the climb, which is not particularly difficult. Further gullies, formed by secondary tearing around the main fault (itself a product of the major disturbance which resulted from the Ochil Fault) extend to the right into Dumyat, and form potential shortcuts to the summit. The first of these, Raeburn's Gulley, is particularly dangerous and should only be attempted by experienced and properly equipped rock climbers, however the second, Siart Gulley, is climbable by anyone of average ability, if care is taken in scrambling up the steep step at the end. The third, fourth and fifth gullies are not named, and become progressively easier.