Again the things that get me out of lurking. I try to take a "You kids just have fun" approach to VampChron fandom these days. And I love what the new VampChron fandom is doing with pretending Lestat is real but y'all are killing me with the lack of basic New Orleans knowledge. Let your fandom elder help you out here:
"The neighborhood was built on an existing unmarked gravesite" - the neighborhood is the French Quarter which is the original city of New Orleans. There has been rebuilding since the city's start due to fires, but absolutely nobody would go "Gosh, what the heck was here before?" because the answer is, depending on the specific address, either "The previous building(s) that burnt down" or "The native villages that were here before the French" or "Fuck all else because this is swampland." There's no version of this where locals would wonder what had been there before. That'd be like you wondering was was in your sock drawer before you put socks in it.
We then get into "unmarked gravesite" which is also not a thing because New Orleans (as we define its geographic borders today) is below sea level. Now then, the French Quarter itself is a whopping six feet above sea level which is among the reasons why Bienville ignored everything remotely looking like common sense and said "Hey, this would be a super great place to build a city which won't ever suffer any problems from being in the middle of fuck all swampland at all!"
But that six feet above, much though it is by the standards of New Orleans nosebleed inducing high altitude, doesn't mean they would have buried bodies there in graves unmarked or otherwise because burying requires having dirt you can put stuff in. Which you cannot do in fuck all swampland because the ground is water. Nothing gets buried, up to and including tree roots which either hug the surface level of the ground or just give the fuck up and grow into the air because they have more common sense than certain French brothers did when looking for, as aforementioned, a great place to put a city.
And part of the reason why you know they didn't bury people underground in the Quarter, in addition to "No, really, we know what was here before because it wasn't fucking much" is that there's the giant fucking cemetery a few short blocks away from Louis and Lestat's flat. You know, the one they included multiple times in the show? The one with all the above ground graves? Yeah. Nobody's putting a house on a graveyard in the Quarter because there were none. You need dirt for that.
Finally, in what part of me almost doesn't want to tell you guys because you deserve the joy of discovering this on your own but on the other hand hey the show's been out for a while now and apparently you haven't found it yet so here ya go, have a Mardi Gras present: The final reason why nobody would scratch their heads at the discovery of bodies around Louis and Lestat's place is that they lived next door to the LaLauries. As in the real world place where actual bodies were found in their house. The joke in original book fandom was that of course Louis and Lestat got away with murder because their next door neighbors were actually worse.
I get that on the show the timeline is moved up but if the idea is "mysteriously discovered bodies" odds are high it's going to be assumed to be spillover from next door.
(All of which doesn't even get into my own personal peeve which is why would Lestat and Louis go through that much trouble when the Mississippi is RIGHT THERE and you could chuck an entire navy fleet of bodies into it and nobody would ever find them again but WHATEVER nobody asked me.)
Anyway, love y'all, glad you're having fun, and if you need help knowing how to write about New Orleans and Louisiana without giving away that you don't know anything about it, I did this writeup for Falcon and the Winter Soldier fans that applies for you guys too. I haven't looked but something tells me there's way too many hills (ie any) in your stories ;)