In a large mixing bowl, combine the rice, onion, garlic, parsley, mint, olive oil, lemon juice, cinnamon, allspice, salt, and pepper. Mix well to combine.
Place a grape leaf on a flat surface, shiny side down. Place a spoonful of the rice mixture in the center of the leaf, near the stem.
Fold the sides of the leaf over the filling, then roll it up tightly from the bottom to the top.
Repeat with the remaining grape leaves and filling.
Place the stuffed grape leaves in a large pot, seam side down, in a single layer. Add enough water to cover the grape leaves.
Place a plate on top of the grape leaves to weigh them down and prevent them from unraveling.
Cover the pot and bring the water to a boil. Reduce the heat to low and simmer for about 45 minutes, or until the rice is cooked and the grape leaves are tender.
Remove the plate and let the grape leaves cool slightly before serving.