The Oberhalbstein Alps or Platta Group are a mountain range in the Alps of eastern Switzerland and northern Italy. They are considered to be part of the Central Eastern Alps. The Oberhalbstein Alps are separated from the Lepontine Alps in the west by the Splügen Pass; from the Plessur Range in the north by the river Albula; from the Albula Alps in the east by the Septimer Pass and the river Gelgia; from the Bernina Range in the south by the Val Bregaglia.
The Oberhalbstein Alps are drained by the rivers Hinterrhein, Gelgia, Liro and Mera.
Wikipedia https://en.wikipedia.org/wiki/Oberhalbstein_Alps
Coordinates 46°29'11.939" N 9°29'34.531" E