Lay-by about 1 mile from the main Pen y fan Car Park. Stayed over 1 night and woke up to a magnificent view across the mountains. It is on the A470 which is busy, so be prepared for a bit of road noise. This is a large lay-by, so you can base yourself a distance from the road. Grassy area to walk a dog on a lead. Two other vans arrived in the evening. No issues and felt safe.