Stair Hole, just to the west of Lulworth Cove, is a remarkable small cove with natural arches cut into steeply-dipping Portland and basal Purbeck limestones. Through these arches and a gap where one has collapsed, the sea enters to erode the softer parts of the Purbeck limestones and shales. Soft multi-coloured Wealden strata slump southwards towards the sea. The most remarkable feature of Stair Hole is seen in the eastern cliff. Here is a cross-section throught the Lulworth Crumple, where small folds in the Purbeck strata are present within the steep northern limb of the Purbeck Monocline.