The actual “downtown” part of Miami [1] is generally not worth your attention unless you’re in town to make a deal. The enormous skyscrapers and apartment buildings are all business, and with the exception of the Jewelry District, there’s not much to see for the casual traveler. However, just outside of downtown proper is the famous Design District [2], filled with galleries and decor boutiques.
Links:
[1] http://www.moon.com/destinations/florida/miami
[2] http://www.moon.com/destinations/florida/miami/sights/downtown-miami/design-district