There is really a lot to do around Osečná, by bike, on foot, by car. You just have to choose... Ploučnice springs, Ještěd, Hamr na Jezeře swimming pool, Židlov nature reserve with bison, Ještěd golf course, Kunratice spa, Ralsko ruins, Děvín, cycle paths, hiking trails, Noviny pod Ralskem gap, Golf Malevil, forests full of mushrooms. You will not be bored.
As part of summer trips with the family, we have one traditional one - a hike to Ještěd. The dominant feature of the Liberec region is definitely worth a visit even in the summer! You can get there by car and park in Světlá pod Ještědem, from where you can set off along the pastures on the red hiking trail. Along the way, we like to pick raspberries and blueberries and compete with the kids to be the first to touch the transmitter. The hike will also be made more pleasant by a short refreshment stop at Chalupa na Pláni, and the main one will come at the top - at the iconic Ještěd restaurant with a well-deserved view of the Liberec countryside. Here, I recommend rewarding yourself after you deserve it, children with schnitzel or ducat buns and adults with beer and sirloin. You can then return to the parking lot by a shorter route along the blue trail. Source: https://www.kudyznudy.cz/vylety/zamilovana-mista-tymu-czechtourismu/letni-vylet-na-jested