Known as the Hollow Mountain, Cruachan is a pumped-storage hydro plant built deep inside Ben Cruachan, its turbine hall carved out of the rock beside Loch Awe. The visitor centre on the A85 has a cafe, shop and free exhibition, and Falls of Cruachan station sits right by the door. Note that the guided tours into the mountain itself are suspended until 2028 while the station is upgraded, so it’s the exhibition rather than the underground trip for now.

© John Myers / Geograph · CC BY-SA 2.0