_Llanymynech Hill_ is an extensive tract of land, on the limestone formation, comprising about 160 acres. It belongs to F. R. West, Esq., M.P., and the minerals upon it are leased to the “_Carreg Hova Copper and Lead Mining Company_.” The limestone rocks, part of which are 900 feet in height, are worked by another Company, and large quantities of fine limestone are annually raised and sold, principally for agricultural purposes, in Shropshire and Montgomeryshire. The ores raised from the hill are carbonates, sulphurets, and oxides of copper, carbonate of lead, and calamine (carbonate of zinc). On the north-west side of the hill are the remains of ancient surface mines, supposed to have been of Roman origin, and from vitrifications near this spot, there is no doubt that the Roman miners smelted their copper there in jars on open hearths. Near these old workings is an immense cave or level, known in the district by the name of the _Ogo_, from the Welsh _Ogof_—(a cave). Its windings are so numerous and intricate, that many years back the labourers, attempting to explore its mazes, were bewildered in the effort, and a number of miners, who had been sent in search of them, discovered them lying prostrate on the ground, in despair of ever again seeing the light of day. Skeletons, various utensils, and coins of Constantine and Vespasian, Antoninus and Faustina, have been found within and about the _Ogo_. One of these skeletons had a battle-axe by its side, and a bracelet of glass beads, like the druidical rings or beads called _glain neidr_, (the _ova anguinum_ of Pliny,) and another with a golden bracelet encircling the wrist. In 1849 two other skeletons were found buried in trenches near the _Ogo_, by the side of one of which lay a strong battle-axe, formed of mixed metal, but sharp at the edge. These skeletons were of a very large size, the bones evidently being those of remarkably tall men. The late Mr. J. F. M. Dovaston explored the _Ogo_ several years ago, and declared that none of the paths extend more than two hundred yards from the entrance. Great quantities of human bones were found in many parts, especially where the cavern becomes wide and lofty, and this fact induced the belief that the place, at some early period, was a refuge in battle or a depository for the dead. For years it was commonly believed in the district that this labyrinth communicated by subterraneous paths with Carreg-Hofa Castle; and some persons have exercised their imagination so largely as to declare that, while in the far recesses of the cave, they have heard the rivers Vyrnwy and Tanat rolling over their heads, and that the said labyrinth actually leads down to fairy-land!