Not long ago I visited slate quarries in Wales and I was amazed how people use this place. Well here is a precedent by Austrian design studio AllesWirdGut Architektur that designed festival grounds inside an old rock quarry in St. Margarethen, Austria. The project covers a vast surface area and features a large series of walkways and bridges which start at the top of the quarry and lead the visitors down to the main festival space. The complex form of the walkways, jutting out from the terrain takes its form from the mining techniques that originally created the space, rusted metal used for cladding contrasts with the light colored stone inside the quarry.

All incredibly beautiful, creating dialogue between the existing topography and the introduced, dynamic form, not only telling the history of the place but also allowing the current events to keep it alive.
More here an here.