The river Simme begins at the Alpine lake of Flueseeli (lit.: Little Lake of the Flue) () on the secluded Alpine meadow just above the Flueschafberg cliffs. But right afterwards, one level and lower, below the Flueschafberg cliffs, on the Alpine meadow called Rezliberg, it converges with several creeks which have even higher springs, such as the Truebbach, the Rezligletscherbach, and the Ammertenbach. This area is located west of the mountain range Wildstrubel, and to the north of and below the Glacier de la Plaine Morte (), and about south of the resort of Lenk. Underneath the Rezliberg it forms the Simmenfälle, several waterfalls, which have, altogether, a drop of .