Oke, it is not Groningen but Appelscha (40km south west) but it is a touristic village, and that is for a reason. The nature around is astonishing, my personal highlight are the inland dunes. Normally in the end of May a local running club organizes a nice run. This year there is the option to run a marathon or semi-marathon, individual or as a duo(swapping from bike to running, bikes can be rent).
The route won’t be marked, but after subscribing you will receive a gpx file. you can pick a desired date/time to start,and the organisation will check if that time-slot is still available. You have to subscribe three days prior to your starting date. For more information (in Dutch) check https://www.lsv-invictus.nl/28-invictus/453-solo-duo-teammarathon-mei-2021 To make it a real competition, there is a 50 euro first price
If you want to have a run with an experienced runner to discuss your ambitions and how to achieve them, sign up for an analyse run