Ilmenau is located within a basin, formed by Ilm river on the northern edge of the Thuringian Forest at an altitude of 500m. The surrounding mountains are the "Pörlitzer Höhe" (573 m) in the north, the "Ehrenberg" (528 m) and the "Tragberg" (534 m) in the east, the "Lindenberg" (749 m) in the south, the "Kickelhahn" (861 m) in the south-west and the "Hangeberg" (701 m) in the west. Whereas the first three belong to the foothills, the last are part of the mountainous Thuringian Forest. There is also a geological border between them: the mountain range is of porphyry and the foothills are of Muschelkalk (in the west) and Buntsandstein (in the east). The Kickelhahn is one of the most visited mountains within the Thuringian Forest and hosts an old viewing tower with a panorama above the town and the forest landscape.