There's much to see along the entire route, including nested village centres, votive chapels, splüi (shelters beneath boulders), "hanging meadows" on boulders, traditional rustici, and grotti serving refreshments. Although electricity is produced in the Bavona valley, there's none here, except in San Carlo: one of the reasons why the valley is uninhabited in winter.
From Bignasco (on the bus route) the red-and-white waymarked path leads to Fontana (look for the arched bridge over the stream). Penetrating further into the valley, you can see, from afar, the la Froda waterfall in Foroglio, tumbling over 100 metres out of the Calnègia valley.
After crossing the wood to Roseto, sections of the path then pass through colourful flowering meadows. The path to Sonlerto is almost flat. You then climb again to reach San Carlo.
Make a note of the bus times for the return journey. San Carlo is at the lower end of the Robièi aerial cableway.