The Cairnmuir Hill Track crosses the hills between Cromwell and Clyde on a route that was used in the 1800's before the Cromwell gorge road was opened up. It's a vast, arid, uplifted landscape with views in all directions.
The track climbs 800 metres (2600 feet), on four wheel drive farm roads. They are steep in places and unless you are very fit and strong you'll end up pushing your bike for perhaps an hour.
There are orange markers to guide you from time to time but best to take a topographical map or an app with downloadable maps such as BackCountry Navigator. The ideal time to go is on a fine, clear, cool day in autumn. Call in at the Cromwell Information Centre before you set out to pick up their walk-bike brochure. It has an excellent description of the route.
The track can be ridden (or walked) both ways. If you start from Clyde try to get a lift up Hawksburn Road which relentlessly climbs 400 (1300 feet) metres in just a couple of kilometres.