Nantglas is devided into two parts - Nantglas Isaf (Lower Nantglas) is a wide adit leading in from behind the railway track to a collapse, and Nantglas Uchaf, (Upper Nantglas) is a collection of adits, shafts and open stopes near the top of the mountain. The Nantglas uchaf adit's entrance is collapsed nearly entirely and a serious scramble on the tummy is neccecary if entering from the collapsed entrance into the original tunnel. Once inside, the spacious tunnel leads quickly to an empty whim chamber housing only an old wheel now. Ahead are the impressive stopes and the level continuing beyond. A ladder remained descending the stopes until recent years. The Nantglas lode was shared with Foxpath mine, but cutting at it from a different angle. See the Rheidol United Mines book by R. J. Prichard.
Up the stopes, and daylight is reached. At the top of the open stope several shafts drop down everywhere and causion must be taken while exploring amungst the moss above the adit. A further adit on the forestry track leads into one of the shafts probably.