I had helped him create a two-sided stairs (see picture) but it wasn't staying together all that well and whenever he put one of his toys on it it fell apart.
So, on his own, he constructed a pillar and attached it to the middle of the stairs, creating a perfect support. The edges were still a little shaky though, so he made two more pillars and placed them on both sides of the original.
I know it's not rocket science, but I love watching him figure this stuff out. Figuring out why one structure stands and one structure falls. Figuring how tall you can make a tower of Duplos before it bends too far and goes tumbling to the ground. Figuring out why some things hook together and others don't fit. It's not like it's even possible to categorize everything he figures out by building, by trial and error, but it sure is fun to watch him. Kids learn through play but also think that learning is play (like learning the Greek alphabet or how to play the piano). I love that he can have both, and they don't have to be in conflict with each other.
"And at the fountain gate, which was over against them, they went up by the stairs of the city of David, at the going up of the wall, above the house of David..."
Hunter is 3 years, 5 months old