The Geisberg is a narrow, elongated mountain ridge in a valley widening of the Middle Moselle.

It belongs to the right-hand side, the Hunsrück facing Moselle Hills, which are part of the Rhenish Massif on the left bank of the river Rhine.

The Moselle continued flowing across the today's course past the Brauneberg mountain, and further in a north-westerly direction through the valley of Osann-Monzel into the Wittlich Depression.

There it turned back south and reached in Lieser the current course of the river again, at 2 to 3 km from the point where these bends began.

At the time of the Lower Terrace, a first breakthrough of the Moselle took place on what was then an impact slope near today's Mülheim.