This area is still known as Clwyd Limestone by climbers, though the county has reverted to its former name of Denbighshire. Most of the crags are south or west facing limestone escarpments - sunny but very exposed to the wind.
The main crags are part of the Eglwyseg escarpment near Llangollen, but there are also some quarries to the north, near Mold. Llangollen lies on the A5, not far from the border with England, so this area can be useful when the main mountain crags of Snowdonia, much further west, are affected by rain.
I climbed here for the first time recently, on the way back from Snowdonia. It's a really beautiful location, and despite it being a sunny weekend there were very few people there. I would highly recommend a visit!