The Fishmine in Bishops Wood (Coed yr Esgob) is one of a series of lead mines that were opened in the area in order to exploit the seams of lead and zinc that were thought to exist in the area. There was good reason to believe this, since nearby Meliden had been successfully mined for minerals from Roman times. The Fishmine was opened in 1724 by the London Lead Company, but never really produced enough to remain profitable. The London Lead Company was a Quaker led business largely based in the Durham area. However, it bought a number of Lead mines in Flintshire (now Flintshire and Denbighshire) in 1695, largely based on the growing reputation for the lead and other minerals in the area. The business was wound up in 1905 in the face of diminishing yields and foreign competition. The Fishmine was leased by the Bishop of St Asaph, but divine inspiration did not, it seems prove decisive. It is thought that the Fishmine gained its name for the shape of the spoil heaps that can be found in the woods and on the slopes below, or from the fish fossils that were sometimes found in the mine.
Today, despite being water filled in places, much of the mine has been explored. It is a draw for cavers and youngsters, some of whom get into difficulty, especially in trying to cross the lake which is almost three metres deep in places. The Fire Service cautions care, having had to rescue several people over recent years.