Walking in downtown Santiago, you will find many shops to buy what you want. Surely, if you are not accustomed to seeing so many people, you'll feel a little overwhelemed in downtown Santiago. There are several streets with made into a pedestrian mall with no traffic where there are large multi-story shops.
Walking through the square (Plaza de Armas) you will find many works of art, at the center of the square, again I must make a recommendation, to keep all your things such as cameras, cell phones, etc. in a safe place, because it is very common for tourists to robbed of this kind of thing.
Prices are quite higher than in the San Joaquin, so before you compare before you buy.
Another thing to consider is that different stores in the same area can have a big difference in cost, strange but true, because I could see for myself .
There are many places to go near the center and the tourist police are very friendly when asked for something. When you have any questions do not have problems, do not rely on strangers is better to ask the tourist police, and so your journey will be very quiet and enjoyable.