Level in the context of "raze" means to make level with the ground, to leave no stone on stone if you want to get all poetic about it, though no doubt a pedant examining the scene, finding one or two stones still atop other stones, might complain that the destruction was not total enough to warrant "raze." Enjoy the language, Nigel. Revel in its poetry and, every now and then, when you feel like it, put up a little fight to preserve its nuance and colour. And stop worrying.