The painting shows a plan of Toruń according to Matthäus Merian from his work "Teatrum Europaeum", 1652. It is accompanied by a small excerpt from Zbigniew Herbert's poem "Three Poems from Memory": 

...The city stands over water as smooth as the memory of a mirror....

While this refers to Troy, it is unclear whether this metaphor was not created by Herbert during his studies at the University of Torun.