I have a friend in my class. He loves to build towers.
He often explores this structure, building them time and time again. Sometimes he balances things on top.
He builds them tall, often trying to build taller than his head.
He had developed a good system of balancing the blocks. He carefully adds a block and often will hold part of the tower with one hand while carefully placing the top block.
I often wonder why he loves to build towers so much. (Of course, the crashing down of them when they fall has a great appeal!)
I've been reading more and more about play, especially self-initiated play. David Elkind says that kids will create play to learn what they need to learn. My friend certainly is developing his skills in physics and engineering.
And he's enjoying all that experimenting and investigating. When I hear his giggles as he stacks the blocks higher (and when they inevitably crash down), I must laugh, too. Because those towers are teaching me, too.