Old Onslow is the original 1885 townsite, left behind when the port moved to Beadon Creek in the 1920s. The gaol, courthouse, police buildings, cemetery, and jetty remains are scattered in a flat, windblown landscape near the Ashburton River.
It is free to wander, but it feels remote. Take water, go in daylight, and expect ruins rather than a polished heritage precinct.