From the railway station Bled lake to the railway station Podhom (only one stop) and then on foot to the entrance to the gorge (approx. 15 min). Followed by a walk through the gorge and the green path across Katarina back to the train station Podhom (approx. 40-50min).
You can also choose to walk to the Vintgar railway station (20-25 minutes) on Blejska Dobrava from the end of the gorge and return from there to Bled.