I went for a walk today which involved me climbing and crossing Cleeve Hill. It was pretty clear, and so I could see, way out to the West, the Skirrid and Sugarloaf Mountain near Abergavenny. Now from doing Spa2Summit I reckon that's probably 35-40 miles. Assuming that I could see the same distance in every direction (which wasn't possible with Cleeve Hill, the Malverns etc in the way) but just say I could, that would mean I could see something in the region of 3800-5000 square miles of ground. That's a lot of ground.