Bodmin Moor is a vast expanse of rugged moorland beauty, that is steeped in history as well as being rich in archaeological remains. The scientific and economic importance is illustrated by the remnants of the 19th century tin and copper mining industry the remains of which still form part of the landscape. The remains of engine houses and mine chimneys are still clearly visible hugging the slopes of Caradon Hill.
Geologically, St Cleer straddles the granite of Bodmin moor and the metamorphic aureole around the granite, which is rich in metal deposits.
The climate is dominated by the westerly winds from the Atlantic, bringing rain and sea-mist. In winter there is usually snow fall on the moors, which may lie for a few days, and in summer the heat is tempered by cooling breezes. In this part of the country spring comes early, with daffodils blooming in the fields and hedges.
The western part of the parish is bounded by the river Fowey, draining off Bodmin Moor in a deep wooded valley. The river rushes down a series of steps at Golitha Falls, as it leaves the upland moorland. Further north a tributary of the Fowey has been dammed to form Siblyback Lake, managed by the South West Lakes Trust. https://www.swlakestrust.org.uk/siblyback
Prehistoric people on the moor have left traces of settlements, field systems, standing stones and burial chambers, the most conspicuous of which is Trethevy Quoit, standing in a field near Tremar Coombe.