Put the potatoes, carrots, zucchini, artichoke hearts, leeks, tomatoes, turnip and celery in a large pot. Add the bouillon cube, olive oil and some salt and pepper. Cover with water. Bring to a boil and simmer until all the vegetables are tender, 20 to 30 minutes. Put the mixture through a food mill or blend with an immersion blender. Reheat to serve.