Central Ilmenau is walkable. The university campus is a longer stroll east of the centre, while the forest sights climb south-west into the hills. For Kickelhahn and Jagdhaus Gabelbach, walking is part of the experience rather than a problem to solve.
Bring decent shoes if you plan to follow the Goethe walking routes. Paths are well marked, but the slopes can be muddy after rain and icy in winter.