High Mountain Mining Heritage of the Picos de Europa (Northern Spain). Las Gramas mining complex, conservation and potential use as a geotourism resource - Gomez-Lende, Manuel; Serrano, Enrique; Jorda-Bordehore, Luis; Sanchez-Benitez, Javier; Millan, Jose Maria; Jorda-Bordehore, Rafael (Geoheritage, 2025)