Mali Graben is a creek and a natural branch of the Gradaščica River in southwest Ljubljana. It flows south of and parallel to the Gradaščica and is the largest affluent of the river Ljubljanica. It is also known as Stržen (literally, 'thalweg') and Mala voda ('Little Creek'). The creek is a natural channel. It splits from the Gradaščica not far from Bokalce Castle, then flows across the southern part of the Murgle residential district and joins the Ljubljanica from the left side near the Gruber Canal. Most of the water from Gradaščica is diverted into Mali Graben, helping to alleviate flooding of the Trnovo District in Ljubljana.