Marianne, I enjoyed the link about the Grande Cariçaie...the marshes interspersed with alluvial forests...they even gave an audio pronunciation for Cariçaie!
I was interested in the 'fairy pyramids' because they somewhat resemble the tufa towers in Mono Lake, perhaps not all that far from where Rooster lives in California! However, the formation is entirely different, as the tufa towers are calcium carbonate, formed because Mono Lake is a terminal lake so when freshwater creeks feed into the salty water of this no-outlet lake, these towers form as a result of the currents mixing!
I am guessing that at Val d'Hérens, the moraines must have been a conglomerate of various kinds of stone which eroded at different rates, leaving behind the sturdier stuff of those towers...?
Oh, btw I found a nice photo of those tufa towers for you, once when I was traveling I stopped at midnight to sleep, and when I awakened in the morning, this was the sight that took my breath away! I camped there at Mono Lake for several days...just stunningly beautiful, fascinating ecology.