The "Alter Hagen" nature reserve is located in the upper Strycktal valley and includes the headwaters and side valleys of the Itter. The state border with North Rhine-Westphalia forms its western and southern boundary and runs along the watershed. A particularly idyllic part of the protected area around the northern side stream is aptly named "Paradise". The marshy floodplains, moor meadows and areas of swamp forest that characterize the area are of central importance for the protection and preservation of this natural habitat.

In the 16th and 17th centuries, an ironworks stood on the Alter Hagen, the exact location of which is still unknown today. The open meadow areas can probably be traced back to the ironworks at the time, which provides a fascinating historical background to this unique nature reserve.

For hikers, the W6 hiking trail offers a great opportunity to explore the lower area of the Alter Hagen. Those wishing to gain a deeper insight into the "Paradies" part of the nature reserve should use the local hiking trail W1.

The Alter Hagen nature reserve is not only a place of historical significance, but also a refuge for many rare plants and animals.
The upper area is characterized by bog birch, alder and rowan, while the rare Nordic purple moor grass, an ice age relict, grows in the transition areas. The brown sedge swamps along the Itter have a high species richness and marsh marigolds, smooth oats and golden oats thrive in the wet meadows. Botanical treasures include coralroot and plane-leaved buttercup.
The wildlife includes the great horned owl and woodcock. The crystal-clear streams are home to brown trout, bullheads and rare snails. Amphibians such as the beautiful fire salamander, 71 different butterfly species and iridescent dragonflies can be admired.