In a large saucepan, combine rice, water and cinnamon stick. Set aside for 3 hours.
After 3 hours, bring to a boil, reduce heat, and simmer for 30 minutes. Allow to cool.
Puree rice mixture in a blender until smooth. Strain through cheesecloth or a fine sieve. Flavor with vanilla and sugar to taste. Chill, and serve over ice.
