In a large saucepan, combine:
225 ml rice, rinsed
2 ℓ water
1 cinnamon stick (about 5-7 cm), broken into pieces
Set it aside for 3 hours. Then, bring it to a boil, reduce heat and simmer for 30 minutes. Leave it to cool.
Puree the rice mixture in a blender until completely smooth. Strain it through a fine sieve or cheesecloth. Chill & serve over ice.