It is 42 kms (26.1 miles) in length and, having now walked the least frequented section (Steeg to Halstatt), I can say that I have now walked along all of it.
The final couple of hundred meters of the path was closed due to a rock fall, but I had been along there before, and so I was more than happy to descend to the UNESCO World Heritage town of Halstatt using the old miners-path and not the modern rack and pinion railway as we had originally intended. It was then a short ferry ride across the narrowest part of the lake to the railway station for the return journey.
The trail follows the course of what is claimed to be the world's first pipeline, a construction comprising hundreds of hollow trees joined end to end and through which flowed a salt and water mixture sent from the ancient salt mines in the mountains above Lake Halstatt all the way down to the Traunsee Lake where the salt was extracted and loaded onto waiting vessels at Ebensee. There are many information boards along the way.
The top picture shows a bridge covered with debris from a recent rockfall. The other picture shows my companion hiding behind a waterfall. Stones, timber, water, sand and clods of earth were all tumbling and sliding down the steep mountainside.
I would suggest the walk be split into two. Walking from the town of Bad Ischl which is situated at the midpoint will offer the best views and be found to be most convenient.
Day 1 - Walk from Bad Ischl to Halstatt and return by ferry/train.*
Day 2 - Walk from Bad Ischl to Ebensee and return by train.
*In my opinion the final 6 kms section between Steeg and Halstatt should not be attempted if less than 2 hours of daylight is remaining.
The walk may be extended to 3 days by catching a train from the suggested base at Bad Ischl to Halstatt Railway Station and from there following the trail via Obertraun to Koppental and thence up through the gorge to arrive directly in front of Bad Aussee Railway Station. From Bad Aussee catch any train in the direction of Attnang-Pucheim and alight at Bad Ischl.