Abstract reasoning: what's missing?

I used to play the "What's missing?" game with my dad, and now you can play it at Bird Park.  Look at empty spots in Bird Park, and asks your child "what's missing?"  This stimulates abstract reasoning, which is particularly useful for children with cognitive disorders.

"What's missing in this parking lot?"  Cars, trees, parking meters are all possible answers.  What answers can your child think up?  Post below!