The Avon River cuts a narrow gorge through the Perth Hills at the 18-sq-km Walyunga National Park, before it morphs into the Swan River as it continues seawards. Bushwalks here include the 5.2km-return walk to Syd's Rapids, the 1.2km Aboriginal Heritage Trail, and the 10.6km Echidna Loop, which has show-stopping views over the Swan and Avon Valleys.
Access is via Walyunga Rd off the Great Northern Hwy, 35km northwest of Mundaring. There's no public transport and no accommodation (day-tripping terrain).
Walyunga has one of the largest known campsites of the Noongar people; the site was still in use in the late 1800s. The area may well have been occupied by Aboriginal people for more than 6000 years.