The market of San Lorenzo is very close to the dome and train station, right in the center of the city, it is just impossible impossible not to find it. The building, built between 1870 and 1874 is one of first in Italy to being realized with modern techniques (for the age…), materials are iron, glass and cast iron, and it has been planned from Mengoni, who designed also the other market of Florence (sant' Ambrogio, a smaller one but also pretty and much less chaotic) and the gallery Vittorio Emanuele II of Milan. The base of the buildinf is monumental, made in stone, very suited to the Florence context, with large round arches; the upper part is light and transparent thanks to the glass a decorated with a metallic structure. The big glasses make the inside of the covered market very lightful.
Externally the market is surrounded with loggiati of classical arches, that turn around along the roads surruonding the building; in these roads you'll find all the external stalls.
The walk among the stalls is usally pretty stressful, the road is often overcrowded, and sometimes covering just 300 meters can take a long time… the stalls are selling just everything, mostly cheap leather accessories, but also t-shirts, souvenirs of Florence (some of them are really kitsch and funny!), clothes... there are also some vintage clothing and some craftsman's shops.
But what I most like of San Lorenzo are the benches of the food market, those situated in the inside. There are butcher's shop benches with wonderful pieces of fresh meat (Tuscay and Florence are well known for it's fine quality meat). Not to mention the benches of the cheeses… Some benches sell jars of the best conserves, like peppers, dried tomatoes, etc... others sell dried beans and cereals in bug raw cotton bags which are so beautiful to see… I love the scents of San Lorenzo, the smell of the fresh blood of the meat (it's a bit creepy but i like it!), the scent of seasoned pecorino cheese and the tasty smell of spices…
I suggest you to visit the market in the early morning, it' less crowded and all the shops are open (food shops are cloesed after 14.oo pm). If you're hungry taste the tipical Florence fast food: bread with "lampredotto" at Nerbone's (inside the market), hot boiled tripe and other offals served in a piece of bread and red wine.
Here are two videos taken from Youtube of the market of San Lorenzo, enjoy!