The city of Matagalpa is nicely situated in the mountains. Hence, there are quite a few hiking possibilities around – including a "Black Forest" (the "Selva Negra")!
The (private) reserve of Selva Negra is especially beautiful. Another hike I did in this region (to Cerro Apante, close to the city itself) was nice as well, but could not compete with the beauty of the "Black Forest".
All in all, the hills and mountains around Matagalpa are indeed worth a visit. In particular, I enjoyed the very pleasant climate here in the mountains – no sweating even when going hiking!