From the railway station, go uphill to the 16th century castle and, up the steps, you reach Serra.
After the carriage road, go along a short mule-track, and then back to the carriage road. Follow the carriage road, to the village of Costella, and then go down the path on the left until, after 300m, you reach the Church of S. Giorgio and after a further 50m, the 3/4 connection with path 3.
Go along the carriage road for 600m and, after the third bend, go up a few steps to a beautiful mule-track, which, after S. Giorgio's stream, leads after 500m to Montaretto village. Near the church, there is path 3, which leads back to Bonassola.