Clearwell Caves 2010

Clearwell Caves and Symonds Yat, two of the spectacles of the Royal Forest of Dean.

Making up the English side of the Wye Valley Area of Outstanding Natural Beauty, the Forest of Dean is an old hunting forest that actually manages to satisfy the current meaning of "forest", by being largely covered with ancient woodland. It is also one of Britain's less-known caving districts, with a few caves on the Welsh side as well (most especially the stunning Otter Hole).

Clearwell Caves are one of a set of spectacular mined caves, and the longest cave in the Forest of Dean, with the shallow part run as a showcave, and deeper parts open to novice tours and experienced cavers. The caves are easily some of the oldest in the country, having formed about 180 million years ago. Some are thought to have been cavities in the shell debris beds that made up the limestone about 280 million years ago, with further development happening after the debris became rock and was exposed. Following that, the caves spent a long time being the conduits for water saturated with iron from overlying beds. The iron ore was deposited in the caves, coating the walls upto a couple of metres thick, or as little as a millimetre.

The caves have been mined probably for centuries - if not millenia - for ochre, with the iron being removed as a less important product. In places, the iron is so loose, it can be literally peeled off the rock with ease. In others, it must be hacked off, which of course removes some of the structural integrity of the rock. What results is a mine with virtually no natural rock surface still visible, and endless evidence of systematic mining. The miners explored all of the known cave, connecting it to various other mines, dropping to 166 metres below the surface. The showcave operators estimate that as much as 30 km of cave and mine may be known, of which cavers have estimated about 24 km is naturally connected cave, taking up about 107 metres of depth.