"I of that city was which to the Baptist Changed its first patron"

(Canto 13, lines 143-144)

"That city" is Florence. There is no consensus on who the speaker is here, and many have suggested that Dante does not intend a specific figure, because of how frequent suicides were in Florence during this time. There have been speculations that the speaker might be Lotto degli Agli, a judge mentioned in historical records at the end of 13th century, who was bribed to judge unfairly in a case and later committed suicide in regret; or Rucco de' Mozzi, who hanged himself after squandering his fortune.

Florence's first patron was the Roman god Mars. After the advent of Christianity, its patron saint instead became John the Baptist. According to early Florentian lore, this would have so angered the god of war that he doomed the city to the never-ending conflicts it was subject to. In Dante's time, there was still an old, broken statue of Mars standing at "the pass of Arno", actually at Ponte Vecchio. Later evidence points to that the statue, which was washed into the river in 1333, was actually not of Mars, but of the Ostrogothic king Totila (by early historians confused with Attila the Hun) who invaded and razed the city in 542, and that nothing but its base remained in Dante's time.