The Alpstein Mountains are a subgroup of the Appenzell Alps in Switzerland. The Alpstein massif is in Appenzell Innerrhoden, Appenzell Ausserrhoden and St. Gallen.
Despite it being rather low when compared to other Alpine peaks, the highest mountain is the Säntis at 2502 metres, the Alpstein, due to their northern "outpost" position only a short distance from Lake Constance (nearly 30 km) are relatively tall when compared to the surrounding area. The range also includes the Altenalp Türm as the northernmost summit above 2,000 metres in Switzerland.
The climate in the Alpstein is characterized by its location on the northern edge of the Alps and the pronounced relief. In the Alpstein, for example, more than 1500 mm of precipitation falls per year, in pronounced dammed areas (Schwägalp) and in the higher areas (Säntis) well over 2500 mm of precipitation.
Geologically, the Alpstein massif is different from the predominantly granitic central Alps. Alpstein Alps are predominantly limestone massif and thus represents a kind of western continuation of the eastern ranges, running between Germany and Austria.
Because of erosions, there are numerous cracks, caves and sinkholes, which prevail in the limestone. Two of the three lakes have no surface drainage: the water of the Fälensees flows by the mountain ridge southwest into the Rhine.
Morphologically, there are three main tectonic folds running from southwest to northeast. Only the Lisengrat, the connection between the two peaks Altmann and Säntis, runs across the main ridges. Small mountain lakes are nestled between these mountain ranges on the Appenzell side in the Alpstein valleys: Seealpsee, Sämtisersee and Fälensee.