The surface of the larger islands is hilly, and the general direction of the ridges is north and south, corresponding to the length of the islands. The inland parts present an undulating surface of peat bogs and moorland, dotted here and there with fresh-water lochs, which accentuate, rather than relieve, the monotony of the landscape. The hills are round or conical in shape and of moderate height, ranging from 500 to 900 feet. Unlike the rounded hills of the Lowlands of Scotland, which are often grassy to the top, most of the Shetland hills are brown and barren, being covered with heather and moss or short coarse grass. Neither have they the rugged grandeur of the Highlands, for the sides are generally smooth and rounded, the result of intense glaciation.

The highest in the Mainland is Ronas Hill, Northmavine, a great mass of red granite, rising to a height of 1475 feet, forming the culminating point of the North Roe tableland, and having the hilly ridge of the BjÖrgs on its eastern side. A long range of hills extends through the parish of Delting, from Firth Ness to Olnafirth; and from the south side of that inlet it extends southward to Russa Ness on the west side of Weisdale Voe. This is the loftiest range, and the southern ridge forms a complete barrier between the east and west side of that part of the Mainland. The highest hill in this chain is Scallafield, 921 feet. Other two parallel ridges lie east of this, the one from the east side of Weisdale Voe to Dales Voe in Delting; and the other from near Scalloway in a north-east direction to Collafirth. There are breaks in these hilly ridges, notably where the county road crosses over near Sandwater, and again between Olnafirth on the west and Dury Voe on the east. The other range worthy of note extends from the Wart of Scousburgh in Dunrossness, with intervening breaks, to the east of Scalloway, where it divides into two ridges, and stretches onward to the east and west sides of Dales Voe. Fitful Head in the south, 928 feet; Sandness Hill in the west, 817 feet; the Sneug in Foula, 1372 feet; the Wart of Bressay, 742 feet; and the Noup of Noss, 592 feet, are conspicuous land-marks round the coast. The island of Yell is hilly, with parallel ridges running north-east and south-west—highest point, the Ward of Otterswick. A range of hills extends along the west side of Unst—highest point, Vallafield, 708 feet. In the extreme north is Hermaness, 657 feet; while on the opposite side of Burrafirth is the still higher hill of Saxa Vord, 934 feet.

In the larger islands the land is generally lower on the east side than on the west; and in many cases the hills are steeper on the west than on the east. Most of the smaller islands are low-lying and grassy, forming excellent pasture ground for sheep.

There are many fresh-water lochs in the islands, the largest being Girlsta Loch in Tingwall, Loch of Cliff in Unst, and Spiggie in Dunrossness. They are nearly all well stocked with trout, which makes Shetland attractive to anglers. Shetland has no streams large enough to be called rivers; but it has burns in plenty, rippling brooks in summer and brawling torrents of brown peaty water in winter, when the soil is sodden with rain or snow.