Very many thanks Mike. That is a wonderful site - I will need help to translate it, but I do see the Duderhof Lake and it does indeed look very lovely.
I know that railway-line. Indeed, it is the same one with the station for Ligova. We stopped at a place called Marienburg (a couple of stops before Gatchina) and walked, what felt like, many miles. It was well worth it because we spent the weekend at a dacha near the banks of a river where wonderful natural springs spouted ie-cold, delicious water through the sand. Everyone bathed in those springs too. It was heavenly there. I can still smell the perfume of the peonies (my favourite flower).
Thanks for bringing back the memories.
tsaria