The Cem (, or in its definite form ), also known as the Cijevna (), is a river that rises in Kelmend, Albania and after nearly half of its length crosses into Montenegro, where it flows into the River Morača near the capital Podgorica. The Cem is fully formed at the confluence of its two tributaries the Vukël Cem and the Selcë Cem. It passes mostly through limestone terrain with many karstic formations. These features of the Cem's basin have their origin in the tectonic activity of the Alpine orogeny, which formed the Dinaric Alps. The terrain through which it flows in its course, is at an elevation of more than and can reach as low as . It passes through narrow valleys and steep canyons, where waterfalls are formed before it reaches the Zeta plain. As it approaches the Morača, the Cem area shifts from a continental climate to a Mediterranean one. The drainage basin of the Cem encompasses and is part of the Adriatic river basin. The first cultural indicators of human settlement in the Cem river basin are from the late Copper Age and early Bronze Age (3500-2300 BC). Illyrian tribes such as the Labeatae lived in the area in classical antiquity. In the following millennia, the area passed under the control of the Roman Empire and its eastern counterpart, Slavic principalities, the Republic of Venice and the Ottoman Empire. The Cem basin was the home of Albanian tribes (fise) such as Kelmendi, Hoti, Gruda and Triepshi until the 20th century. Today, the river is divided between Albania and Montenegro. The Cem is one of the last free-flowing rivers in Europe. The river's basin is a source of very high biodiversity, and hundreds of plant and animal species live along its banks. Mammals include wild boars, brown bears and red foxes. The river's canyon is an Important Bird Area for species like the short-toed snake eagle and the Levant sparrowhawk. The marble trout is one of the 22 fish species in the river, which consistently ranks as one of the least polluted rivers in Albania and Montenegro. In the 21st century, it is threatened by industrialization, the installation of small hydropower stations and the effects of climate change in Europe. Name The Greek geographer Ptolemy was the first to mention the Cem as Kinna in ancient Greek. In Tabula Peutingeriana a location named Cinna in Latin is