There is some very scenic running along the Swan River in south Perth, with multiple distance options along more than 10 km of paved multi-use path. A good anchor point is Alfred Cove. A path heads north along the river of the Applecross Foreshore, through Tompkins Park, for 4 km to the Applecross Jetty (great views of the Perth skyline), and another 1.3 km to the top of Heathcote Reserve. So this would be a nice 8 km or 11 km out and back!
Another option (or a longer run!) is some pleasant riverside running in the tony Mount Pleasant neighborhood. From Heathcote Reserve, run south past the Canning Highway, along a riverside road called The Esplanade, as far as the Mount Henry Bridge Reserve at Highway 1. It’s 5 km one-way along a paved roadside path.
We also recommend a jaunt around the Mount Pleasant neighborhood. This is one of Perth’s poshest residential areas, so it’s fun to create your own route along the shaded streets lined with gorgeous homes.