1/4 cup shaved or grated parmesan cheese, for garnish (optional)
Heat the olive oil over medium heat in a large pot. Saute the onion and celery until they start to soften, about five minutes. Add the carrots and garlic and cook it all another few minutes. Add 5 cups of water and bring the pot to a boil. Reduce the heat to maintain a gentle simmer. Simmer the vegetables for 30 minutes.
Add the cilantro. Using a stick blender, puree the vegetables until the soup is smooth. Season with salt (start with 1 teaspoon and add more to taste) and black pepper. Just before serving, add the lime juice. Top each serving with the cheese.