In my past, you on the other side of the glass
Of my memory's museum
I'm just saying, hey Mona Lisa come home
Right now, he feels separate from her, as if they are divided by a sheet of glass (in the Louvre, the Mona Lisa is one of the only paintings embedded in glass for protection)
Also is referring to how he can see the beauty of the girl, but he cannot touch her much like people can’t touch the Mona Lisa. So she in fact is in his “memory’s museum” something to picture but never touch.
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