This is a great question, and I bet lots of my fellow bloggers will have some great routes to tell us about.
My story is different, as usual! I learned to ride in the beautiful parkland that surrounds the National Trust property Dyrham House. Over a hundred acres of parkland, with some very steep hills which were great for galloping up. The only rule was we were not allowed to startle the herd of deer. Totally spoiled me for hacking anywhere else! The park is surrounded by a wall that's at least 5 feet high which mean loose ponies couldn't get to any roads, so we were really relaxed and learnt to stay on, or walk quite a long way to catch your ride!
It's so sad that there is no riding in this beautiful place anymore. Those of us who learnt to stick with our pony partners out there didn't know how lucky we were.