I heard about this site on the web where you can map walks or runs that you have done or plan to do. I’ve had a go and you might like to try a short route along Doncaster Road from the leisure centre and around the back of the Earth Centre site or the run that I used when I trained for the Donny half marathon a few years ago. Here are the link
One word of warning, if you plan to do a half marathon then you need to build up to about 3 laps of the training run, I didn’t find it fun but I guess some people do!
If you want to map your walks and runs visit http://www.mapmywalk.com/ and if you then add the link to your route in a comment I’ll add it here.