Green Bridge of Wales

The geology of the area is composed of a very thick layer of Carboniferous Limestone. Erosion has dissolved the limestone. The weakest parts of the cliff are the first to be worn away. This has resulted over many millennia in the creation of many unusual landforms. In the case of the Green Bridge of Wales, erosion has taken place on both sides of a small headland, caves have been formed which extended further and further until they met, forming the arch that can be seen today. The bridge is about 24 m high with a span of more than 20 m.