It is a delightful short walk of a mile or so along the cliff tops from St Ives to Carbis Bay in Cornwall. In spring the path passes through a tunnel of fresh foliage, wild flowers, and dappled light. You can look down onto the long inviting stretch of clean white sand of the bay long before you reach it. The beach is backed by steep cliffs mostly of dark greenstone (which is metamorphosed basalt from the Devonian period) and houses cluster on the hill above it.
At shore level there are several (I think seven in all) man-made openings in the rock face. These are adits. Adits are horizontal or near-horizontal tunnels into the rock which give access to mine workings or allow drainage from them. Copper and then tin were mined here in the late 19th century and there are numerous shafts and entrances in the hillside above which are now obscured and hidden by the housing development.
Apart from the allure of these mysterious tunnels for cavers and explorers, the entrances form interesting micro-habitats where ferns, mosses, liverworts, filamentous algae, and moisture-loving flowering plants cluster and thrive on the shady rock surfaces where surface-water continually drips down.