Plot Help-Term Needed

[Inverarity]

Why can't it be Unplottable just because it's surrounded by Muggles? If the wizards were there from the beginning, they could have made it Unplottable and cast Muggle-Repelling Charms which over time cause it simply not to be noticed.

In Book Three of Alexandra Quick, it will be seen that San Francisco (which is a fairly small and very crowded city) actually has an extra hill that Muggles don't know about, because wizards settled there when the city was still new, and put charms on it to keep Muggles from noticing. It's possible that if Muggles were specifically looking for terrain features that have somehow gone unmapped, they could do a survey and realize something isn't quite right, but why would they?

Now if you want wizards to arrive and just suddenly stick a secret magical school in the middle of a metropolitan area, that's more problematic. In that case, I'd say they have to create a plausible facade for it, backed by spells that prevent Muggles from questioning the external appearance or investigating further.

[Racing Co]

Here's the frightening part of making magical places out of broken-down buildings: what if the Muggles decide to tear it down. In the U.S., there's often not a huge need to save old, sorry-looking stuff. If St. Mungo's was in a large American city, that place would have been flattened by a wrecking ball in no time. Maybe it's that way everywhere, but I can only speak from my perspective.

I just don't think you'll have quite the same security hiding magical buildings within the veneer of old buildings. At least, I doubt that would make for long-standing protection.

It seems to me that it'd be easier to hide a magical place inside private property because there'd probably be far less tampering. I don't think a spell would permanently stop Muggles from wanting to place a Starbucks in an apparently unused building. Now, if the wizards somehow make a building look like a legitimate, functioning company on the outside, that's another matter.

[OliveOil_Med]

Here's the frightening part of making magical places out of broken-down buildings: what if the Muggles decide to tear it down. In the U.S., there's often not a huge need to save old, sorry-looking stuff. If St. Mungo's was in a large American city, that place would have been flattened by a wrecking ball in no time. Maybe it's that way everywhere, but I can only speak from my perspective.

That's why I'm think of just making it an ordinary-looking house, just like any other. Hide it in plain sight.

Trust me, people do not like old things in the U.S! There are laws, people start committees, and just become general pains whenever they see something they don't like.

[Halgy]

It would probably be possible to jinx city planners into not tearing down your magical dwelling.

In any case, just have some angry old man sit in a rocking chair on the house's front porch. If muggle kids get to close, a rousing "GET THE HELL OFF OF MY LAWN" would fix 'em.

And get some crups (they look like Jack Russel terriers, but with a forked tail that could be magically hidden or altered to look normal); they're only fierce to muggles, so they would act like guard dogs and leave the students alone.

[A.H.]

Just found this in the HP Wiki:

Salvio Hexia

Pronunciation: SAL-vee-oh HECKS-ee-ah
Description: Provides some form of protection against hexes.
Seen/Mentioned: Harry and Hermione cast this spell to strengthen their campsite's defences against intruders in Deathly Hallows.
Suggested Etymology: Latin salvus meaning "safe"[13] and English hex meaning "a magic spell".[23]

So perhaps something like 'Salvio tutela' which is "Safe guard" or 'Salvio deinvado' which is 'Safe from entering' (translated roughly, as I don't know Latin).

/Ari

[TheCursedQuill]

What about just hiding it as... well, a school?

It could be seen as a very prestigious private school, which would make it private property and most muggles would therefore stay away from it. You could also have anti-muggle charms on it, just to be safe. And if any muggle family did try to get their child into the school, they could simply recieve a rejection letter saying that they did not meet the requirments to attend. Eventually, people would just stop trying to get their kids into the school since it has a reputation of being for the "upper-class person".

This would also hide the fact that 100+ students would be walking into it. In a muggle populated area, I think the safest way to get them inside is to just walk in. A portkey would have to be placed far from muggle eyes so as not to raise suspicion, and flying seems a little too risky for that amount of people. And no one would ever think of tearing it down as it's a well-functioning shcool.

Just throw some fence around it, a couple muggle replelling charms, a 'Salvio tutela' as suggested by A.H. and you've got a School for magic, disguised as a school.