Gallt yr Ogof
A useful NE site, but a very long walk up.
Parking is usually by the "RAC boulders" in the Mymbyr valley to the south of the site and the walk up is essentially just up the hill, following what few paths you can find. It is also possible to walk up from Capel Curig, but this is a longer route.
Be aware that the Ogwen Valley is very busy with jets during the week so please use the CANP system.