One of my favourite places to walk, Rutland Water. I've devised several circular walks close to the reservoir and I like to do the full circular walk once a year, which I did in July this year (2012)
You have the option of walking around the reservoir, officially 17m, or you can add the Hambleton Peninsula route, officially making 26m. However I've measured these routes and found them much shorter (I believe the full walk with the peninsula is more like 21).
Either way, it's difficult to lose your way - the paths are mostly surfaced and well-signed. The views are beautiful and the walking includes waterside, woodland, lanes and villages.
More photos from this walk in July 2012 are here
I've published more information about the full circular Rutland Water route here
This time I made a video while walking - take a turn around the reservoir with me!