The Lavant River flows through the valley, having its source on the Zirbitzkogel in Styria and discharging into the Drau near Lavamünd. It is divided into the Upper Lavant Valley (), which lies north of the Twimberger Graben, and the Lower Lavant Valley (), which is further south. The lower, broader valley nestles between the mountains of the Koralpe and Saualpe. The Upper Lavant Valley lies between the Packalpe and the Seetal Alps.