In large, heavy-bottomed saucepan, heat olive oil over medium heat. Add onion, celery, and garlic and stir to coat with oil. Sauté for 5 minutes, until onion is just beginning to soften. Stir in beets and carrots. Sprinkle with salt, bay leaf, and thyme. Add enough water just to cover vegetables. Bring to a gentle boil. Cover, reduce heat, and simmer for about 10 to 12 minutes, or just until vegetables are fork-tender.

Meanwhile, make horseradish-dill cream. In small bowl, combine yogurt, horseradish, lemon juice, syrup, and salt. Stir to blend. Add more horseradish to taste if you wish. Stir in dill. Set aside.

When vegetables are tender, drain and transfer to large, shallow serving bowl. Remove bay leaf and thyme stems. Cool until no longer hot, about 15 minutes. Scatter with pomegranate arils or grape halves and nuts. Drizzle with horseradish-dill cream and scatter additional fresh dill over top. Serve at once.