Formed by the merger of Byala and Cherna Mesta which spring from Rila Mountain. The river passes through the central, lowest relief part of the municipality, running from north to south and collecting the waters of small and larger water streams flowing along the northern and eastern slopes of Pirin. In Bansko Municipality, the Mesta River receives 5 larger right tributaries (Ruzhdavitsa, Dobrinishka, Bezbozhka, Retije and Lakinska) and three left (Zlataritsa, Matenitsa and Gradishka reki). Mesta River runoff is relatively stable. It is cross-border river and flows into the Aegean Sea, crossing the Greek border.