It's pretty straightforward to hire mountain bikes in Kobarid. One of the best places to get a well-maintained machine is Positive Sport on the North West side of town. The staff can show you some potential routes, taking in a mixture of trails and minor roads, around the Natisone Valley. As it's pretty hilly in these parts, the going can get tough, if you don't opt for an electric bike. Either way the scenery is pretty special and you can dip into the local rivers to cool off.