Our verdict
Industrial archaeology doing a very good impression of a nature reserve. The black slag still won't grow grass two thousand years on, which is the whole story of Mendip in one valley — walk it with Velvet Bottom and Ubley Warren and you get the best joined-up wander on the plateau.
The lumpy, pool-dotted valley below Charterhouse where the Romans mined lead, its slag heaps and flues now softened by trees and wildflowers. Paths link straight into Ubley Warren and Velvet Bottom for a classic mining-country circuit.
Nature reserve on old Roman and Victorian lead-mining ground. Keep dogs close and stay on paths — the spoil heaps and gruffy ground are toxic to grazing and hide real holes.