Defintion of wen from the Oxford Dictionary: a boil or growth on the skin, and (archaic) a very large or overcrowded city.
Following the sonnet form of "The Hamam," the four pentameter quatrains of this section describe the old and modern sections of Istanbul, separated by the "mirror of the Bosphorus." (The description recalls the city descriptions in the "Related Verses" section of this site.) The poem is interrupted after the first quatrain by a prose description of the wen on a beloved grandmother. Manuscript 4 is dated "Istanbul. 21 March. I."