Apologies in advance -- I don't mean to turn this into a Lego blog -- but I have to show off my masterpiece!
It's a Lego tree-house.
Or, more precisely, it's a Lego stone house built into a tree.
I didn't have enough brown pieces to make it just a tree house, but I got some interesting new grey cave-wall type pieces when I bought a sack of 1 Kilo of used Legos from a second-hand store.
My 7-year-old Leo helped out by making some of the bushes and the little ducks in the stream. He was an enthusiastic participant right from the beginning, even helping me wash and dry the used Legos.
[me: I felt so Swiss, carefully scrubbing all those Legos with a toothbrush! my husband: Yes, that was very Swiss of you.]