Juxtaposition (Noun):

https://www.merriam-webster.com/dictionary/juxtaposition

the act or an instance of placing two or more things side by side often to compare or contrast or to create an interesting effect.

As the man walked down the he couldn’t help it but juxtaposition the buildings he passed by saying this used to this that Or saying how this building looks a lot like the other or this building has more curves or is flatter has more levels less levels than the other building .