Hi Frank,
Cwmorthin is as beautiful as ever, have a look at this Google maps image of the top of the village:
https://www.google.co.uk/maps/@52.9898266,-3.962552,502m/data=!3m1!1e3
You will see the car park at the lower edge of the heap of slate waste, there is room for about ten cars to park. There has been talk of theft from cars parked there, but we haven't yet seen any evidence of it and go walking in the area often. From the car park walk up past the slate tip and onwards with the river to your left until you come to Cwmorthin lake, shortly after passing the row of derelict cottages. It is no longer safe to cross the bridge over the river lower down due to collapse of the base, but with local knowledge there is a way to access the area, and then to walk up through the quarry levels from where there are plenty of adits with easy access or views into them at least!
To the right of the lake there are some buildings, and a little further round you will find the (gated and locked) entrance to the mines, used by the "Go Below" company for their guided underground tours.
Follow the main track around the left of the lake to pass the remains of the old chapel on your left, then a bit further on the remains of the Plas or mansion, the mine manager's home as was.
Continue forward on the track and up the hill to the remains of level 9 of Rhosydd quarry, (
http://www.penmorfa.com/Rhosydd/description.htm) where there is a lot more in the way of industrial remains in various states of decay, along with a very easy level entrance to one of the adits of the mine. A little further on you will find a fantastic view down Cwm Croesor to the village of Croesor, and an extremely long tramway down as the owners of Cwmorthin quarry would not allow the owners of Rhosydd quarry to carry their slate out in that direction. See this interesting article by Dave Sallery:
http://www.penmorfa.com/Rhosydd/transport.htm
We no longer put bricks through windscreens as we can't be sure the English car doesn't belong to a Welshman, and no longer "keep the home fires burning" either


Take care if you go, and enjoy. Bear in mind the weather is occasionally inclement in the area

Could be good for a TP outing, I would be happy to put on a tour after Christmas - if anyone is interested reply to the thread.
David.