The Maribyrnong River ˈmærəbənɒŋ is a perennial river of the Port Phillip catchment, located in the northwestern suburbs of Melbourne, in the Australian state of Victoria. The Maribyrnong River draws its headwaters from near Mount Macedon within the Macedon Ranges, part of the Great Dividing Range. Formed by the confluence of the Jackson Creek and the Deep Creek below , the river flows generally southward, joined by two minor tributaries before reaching its confluence with the Yarra River at , to eventually empty into Port Phillip. The river descends over its course. The head of the Maribyrnong catchment is situated in the Macedon Ranges region of central Victoria around northwest of Melbourne City Centre. Various creeks beginning in the southern Mount Macedon area flow into Riddells Creek which in turn flows into the Jackson Creek. The Jackson Creek starts its journey northwest of Gisborne, north of Melbourne CBD. The other major tributary of the Maribyrnong is Deep Creek, which also has its headwaters in the northern and eastern parts of the Macedon Ranges. The creek has cut a deep valley through the surrounding basalt plains in its southward course, in particular as it flows through localities such as Konagaderra and Bulla. To the west of Melbourne Airport the tributaries of the Jackson Creek and the Deep Creek conjoin to form the Maribyrnong River. The Organ Pipes National Park can be found adjacent to the Jackson Creek, near the Calder Freeway, with picnic facilities and a prominent display of basaltic columns a geological formation, so named because they look like organ pipes. The river flows south and west. At Keilor the river winds back on itself in a giant horseshoe bend, before winding south again at Brimbank Park. Here the river flows below the western plains. Brimbank Park forms a huge amphitheatre in the bend in the river with picnic areas, cycle and walking trails, and a café, that is usually busy on weekends and public holidays. The area is rich in birdlife and native fauna.