Just south of the center of Tours, there’s scenic running combining paths along the Cher River and several parks. Here are a couple of options, which can be combined in numerous ways. There are kiosks with maps in the area.
Parc du Lac & Parc Honoré de BalzacParc 10k. Start just across the Pont du Lac (bridge) near the Aquatic Center, ~3 km south of old town Tours. The loop around Lac de la Bergeonnerie is ~2 km, on nice paths with water views and a park-like atmosphere. Then, head east along the path along the Cher River, to a small bridge that crosses to Parc Honoré de Balzac, a large park with fields and paths. Run the ~2.5 km loop of the park, and then cross over the bridge at the east end of the park to the path on the north side of the Cher River. Run west for 2.3 km on the pretty, riverside Prom. de Florence. (option: do a little tour of the scenic paths in the Jardin Bouzignac). Complete the route by taking the separate pedestrian path along over the Pont de la Vendée.
Parc de la Gloriette. Just west of Parc de Lac, follow the the Chem de la Pont aux Oies path along the Cher River for 1 km to Parc de la Gloriette. There’s a nice path alongside fields and a golf course (following the Loire a Velo signs is a good idea). This can be combined with the Parc du Lac route above.