Its source and headwaters gorge are situated deep in the Dinaric Alps at the base of the Zelengora and Lebršnik mountains, specifically under the Gredelj saddle. The river source is at 1,227 meters above sea level and consists of five small and distinct wellsprings. On its 90 kilometers course through the first section the Neretva cuts two distinct deep and narrow canyons and two distinct wide and fertile valleys, around Ulog and then around Glavatičevo, before it reaches town of Konjic. This section is also better known as the Upper Neretva (), and here river flows generally from east-southeast to north-northwest as do most Bosnia and Herzegovina rivers belonging to the Danube watershed, and covers some with an average elevation of 1.2%. Right below Konjic, the Neretva again expands into a third and largest valley which provided fertile agricultural land before it was flooded by large artificial reservoir, Jablaničko Lake, formed after construction of a Jablanica Dam near town of Jablanica.