The main watercourses in Ljubljana are the Ljubljanica, the Sava, the Gradaščica, the Mali Graben, the Iška and the Iščica rivers. From the Trnovo District to the Moste District, around Castle Hill, the Ljubljanica partly flows through the Gruber Canal, built according to plans by Gabriel Gruber from 1772 until 1780. Next to the eastern border of the city, the rivers Ljubljanica, Sava, and Kamnik Bistrica flow together. The lowest point of Ljubljana, with an elevation of , is located at the confluence.