Livorno is a gritty city with a long and interesting history. In the early Middle Ages it alternately belonged to Pisa and Genoa. In 1421 Florence, seeking access to the sea, bought it. Cosimo I de'Medici (1519–74) started construction of the harbor in 1571, putting Livorno on the map. After Ferdinando I de' Medici (1549–1609) proclaimed Livorno a free city, it became a haven for people suffering from religious persecution; Roman Catholics from England and Jews and Moors from Spain and Portugal, among others, settled here. The Quattro Mori (Four Moors), also known as the Monument to Ferdinando I, commemorates this. (The statue of Ferdinando I dates from 1595, the bronze Moors by Pietro Tacca from the 1620s.)
In the following centuries, and particularly in the 18th, Livorno boomed as a port. In the 19th century the town drew a host of famous Brits passing through on their grand tours. Its prominence continued up to World War II, when it was heavily bombed. Much of the town's architecture, therefore, postdates the war, and it's somewhat difficult to imagine what it might have looked like before. Livorno has recovered from the war, however, as it's become a huge point of departure for container ships, as well as the only spot in Tuscany for cruise ships to dock for the day.
Most of Livorno's artistic treasures date from the 17th century and aren't all that interesting unless you dote on obscure Baroque artists. Livorno's most famous native artist, Amedeo Modigliani (1884–1920), was of much more recent vintage. Sadly, there's no notable work by him in his hometown.
There may not be much in the way of art, but it's still worth strolling around the city. The Mercato Nuovo, which has been around since 1894, sells all sorts of fruits, vegetables, grains, meat, and fish. Outdoor markets nearby are also chock-full of local color. The presence of Camp Darby, an American military base just outside town, accounts for the availability of many American products.
If you have time, Livorno is worth a stop for lunch or dinner at the very least.