I fancy a trip to nyth y gigfran mine
It's virtually inaccessible from the Ffestiniog side, has to be reached from Cwm side. Can be accessed from the Oakeley pit by entering the adit for floor 8.
Really not much to see to be honest, barely worth the immense effort required to reach it.
Besides, it's owned by Welsh slate and they don't allow access. They won't take kindly if the see you roaming around up there...
Beneath my steely exterior beats the heart of a dashing hero