In my opinion, this is an under-appreciated part of the beach. The boardwalk spans from 47th down to 5th street, where you can then transition to the beach and walk down to SouthPoint. But most people only walk from 15th street to 5th. In my opinion, the best part of the walk is from 23rd street (from 20th-22nd is closed off for construction) to 47th. It's a wooden boardwalk, where biking and rollerblading is restricted, and most of the people abide by this rule. You actually see the water and you get much more of a mix of locals who use the boardwalk to run, walk or just to get out and enjoy the scenery.
Here are a few pictures of our walk:

(ok, this wasn't on the boardwalk obviously, but right before we crossed Collins. Definitely an 'only in Miami' moment for me)

The kite surfers were all up-and-down the beach. You have to love an area where you can get in the ocean all year 'round! We actually sat on the beach and watched them for awhile.

There is much more foliage on the dunes, including large succulents and small trees. This was my favorite shot.
