This now-semi-parking-lot Piazza was inaugurated in 1901, and named(for the third time) after the battle of Mentana in Lazio in 1867. The monument situated here is in honor of Italian soldiers fallen in the battle led by Garibaldi. It was originally called Piazza delle Travi because here was the deposit for the logs that would come from the forest areas from upriver(Casentino and Vallombrosa). There was a little port here that was taken down in the 1200’s when the Rubaconte bridge was built(now called Ponte alle Grazie). By then the piazza had been re-named Piazza d’Arno. I understand Firenze is tight for parking spaces but his little piazza has great history and thanks to its Arno view it has also some potential for a nice relaxing viewpoint of Oltrarno. Hopefully one day they will make this Piazza not a parking lot, as was luckily the fate of Piazza Duomo and Repubblica.