The Italian city on the Arno is Florence, which has 8 letters. Florence is the capital of the Italian region of Tuscany and is one of the most populous cities in Italy. It is known for its rich history, culture, and art, and is home to many famous works of art, such as Michelangelo's David. The city is also known for its beautiful architecture, including the iconic Ponte Vecchio bridge. The Arno River runs through the city and is a popular tourist destination.