1. Reserve a few small blueberries for garnish. Place remaining berries in a large saucepan and pour in 1/2 cup water. Stir in honey and cinnamon. Bring to a simmer over medium-high heat, about 5 minutes. Cook, stirring occasionally, just until berries start to soften and give off liquid, about 2 minutes. Transfer to a bowl and let cool slightly. Puree blueberry mixture in a blender until smooth. Transfer to a large bowl, cover and refrigerate until thoroughly chilled, at least 2 hours.
2. Combine 2 Tbsp. yogurt, lime juice, lime zest and sugar in a small bowl. Stir to blend, cover and refrigerate until ready to serve soup.
3. Just before serving, whisk remaining 1 3/4 cups yogurt into blueberry mixture. Ladle soup into chilled bowls. Drop 2 tsp. of lime-yogurt mixture into center of each bowl. Use tip of a sharp knife to make decorative swirls. Garnish with reserved berries and serve cold.