Knowledge of the past and a great imagination
While walking my 6 year old to school, we play a game we made up called 'Ancient Times.' He'll pick a time in history, for example, The Ice Age. Then we'll describe what we see. He'll pretend to see a woolly mammoth behind a parked car or a glacier behind a tree. It is such a great way to inspire imagination and to learn about history. Of course, the times don't have to be that 'ancient' or impersonal. You could also play 'The time mommy was a kid' or even more fun 'The time grandma was a kid' and he could tell you what he would see then -- or what he wouldn't see -- like people walking with cell phones and iPods!