More like 3.5. An engineer, Nonius, is tasked by Agrippa to bring water to a slum section of the Sebura, a "red-light district", without demolishing any of the houses there. He becomes infatuated with a concubine of a senator who is blocking the completion of his task. He is distracted by her, and also by the senator's wife, and goes to court to prove his lady love, Amaris, is freeborn. Because Agrippa feels he is not the man for the job, he is taken off it, and his foreman is put in charge. The foreman, Byzantus turns out to be inept and he is reinstated. Amaris reveals her true feelings for Nonius when he mentions marriage. I really didn't understand Amaris' psyche except maybe her selfishness and really, that of many of the characters showing the same emotion; the "river through Rome" being desire, which all characters exhibited in one way or another.
I thought the story about putting in the feeder pipes interesting, as well as the descriptions of Rome, but I really disliked the pages and pages of very graphic descriptions of sex and the gruesomeness of the one character's gelding. I did like the last few pages, with the ending. Recommended with reservations. ( )