Watermelon Limeade

Yields about 6-8 small glasses
1 1/2 cups of water
1/2 cup of sugar
1/4 tsp of lime zest
1 cup of lime juice (from 7 limes) 
1  (3-pound) watermelon, trimmed and cubed (I used a quarter of a 12-pound watermelon)
2 sprigs of rosemary (optional)
Place 1/2 cup of sugar, 1/2 cup of water, and lime zest in a small saucepan over medium-low heat.  Stir mixture until the sugar is dissolved. Take off heat and add to lime juice and stir.
Grab a colander or sieve and line it with a cheesecloth.  Then place it over a medium or large bowl. Dump the lime juice/sugar mixture through the cheesecloth to catch any lime zest.
Purée watermelon cubes in a blender or food processor with 1/2 cup of water.   Dump the puree into the cheesecloth and let it drain for 10 minutes. 
When all of the watermelon purée has been strained, gather up the corners of the cheesecloth and twist them together to trap the dregs inside. Squeeze the package firmly to expel all the remaining liquid.  Add remaining 1/2 cup of water and mix well.  Add 2 sprigs of rosemary and cover bowl.  Refrigerate for 2 hours to chill.
Serve with lime and rosemary garnish.