Combine blueberries, sugar, water and cinnamon in heavy medium
saucepan. Stir over low heat until sugar dissolves. Increase heat and
bring to boil. Reduce heat to low; cover and simmer 3 minutes.
Uncover and cook until berries are tender, about 2 minutes. Remove
from heat; stir in raspberries. Transfer to bowl. Cover and chill
until cold, about 5 hours. (Can be made 2 days ahead. Keep chilled.)

Discard cinnamon stick from sauce. Spoon 1 T berry sauce into each of
6 glasses. Add scoop of frozen yogurt and top with berry sauce. Top
with another scoop frozen yogurt and more berry sauce.