Kleven is a distinctive rift valley in Rutsker Højlyng, located northeast of Klemensker. The valley was shaped by the forces of the Ice Age and is characterised by rock walls, depressions and varied terrain. The former railway line between Klemensker and Rø once ran through Kleven and today serves as a cycling and hiking path following the course of the valley.
At the bottom of the valley lies Spælinge Mose, formerly known as Spælling Myr. The bog was used for peat cutting, especially during the World Wars, and today appears as a wetland with damp areas, reed beds and small open water surfaces. At the southern edge of the bog stands Storeborg, a prominent rocky knoll containing traces of an ancient refuge fort. The rock was partly blasted away during the construction of the railway in the early 1900s, but remains of the fortification can still be seen, and the site offers views across the bog.
Kleven and Spælinge Mose form part of a larger protected area in Rutsker Højlyng. Here, rift valley, rock formations and wetland meet in a continuous landscape that can be explored on foot or by bicycle along the path following the old railway.
