Chicago is Like Lasagna is Like Our Aviary

K is visiting Chicago. She realized that Chicago has a river, streets, bridges, more streets, then buildings, layered on top of each other, before the buildings start shooting up into the sky, is something like our aviary.  That is, there are perches at many different levels, food at several different levels, and lots of criss-crossing. It reminds me of how you make lasagna.