I've helped organised a race and the organisers of the Salisbury 54321 blew me away. There's a choice of 5 distances with a mix of runners and walkers for both, they all have different start times, and it all went like clockwork. I'm not sure if anyone got lost but it would have been hard to do with the wonderful route markings and marshalls. My favourite was 'Follow the string through the Yew Woods'.
The route is a mix of country roads, easy trails, and - at the end - the Cathedral and centre of Salisbury. There was endless fields, farms, quaint little villages, and even a castle. It was affordable and all to benefit the local fire services who provided bag storage, toilets, and space for registration.
Not much local support as this was technically a trail race, but the owners of the castle let the race route go through their private estate and the tourists applauded as we ran past the cathedral. The views along the way were pretty rather than spectacular, but on the plus side this meant we didn't have to run up any mountains.