"Usually the subject matter of the image is not the subject of the work" (Roni Horn, contemporary American visual artist).
Yes, it is the Prudential Building with a matrix of windows. It reflects in The Bean and you can see the top slice of it at the bottom of the image.
This is the subject matter.
But what is the subject of the work? What am I trying to tell you?
Let me tell you a story.
Saburo Hasegawa, famous Japanese calligrapher and artist, was giving a lecture to a group of American students at the university about haiku and the vocabulary of Japanese aesthetics.
He started off with the importance of the concept of yugen. Yugen is when the cranes are flying above and you can hear them but the morning fog obscures them and they fly off into the distance and suddenly there is only silence left behind. That’s yugen.
He presented the next concept to understand, which is furyu. And furyu is like when a person in a boat is calling out to another person who's on the shore and they're having a conversation but they can’t see each other. That’s furyu.
Saburo Hasegawa went on like this for some time but eventually one of the students got really frustrated with such nebulous definitions. He raised the hand and asked: "Mr. Hasegawa can’t you tell us exactly what you mean by giving us definitions for these terms?"
Saburo Hasegawa slammed the desk, stood up and said: "What's the matter with you Americans, can't you feel?"