nobody stopping you to do that if that's what you wanted.
but honestly? in my opinion that's just a dumb idea.
you said it yourself, it's a codename for the villain. which means it supposed to be represent something
i mean, what the heck does it means by codename Rome anyway, if you want to named the villain with a codename after a certain location, then at least named it after a river, or a hill, or something else. like Tibir river for example. because it's a river that connect between busy area and cathedral, it's impying that this guy hold the power on the country religious figure in the shadow.
that's how you supposed to use a villain codename so the reader could feels relate to it. not just giving a random name just because you think it's goddamnit cool and edgy. people will forget about it in a few seconds that way.
but then again, like i said earlier. nobody stopping you if you wanted to do that, you do you.
