[Oh, so he knows of Mario. That helps a little.]

There's an old, half-constructed building near my school. One of the stairways inside wasn't finished yet, either.

Did you know? Stairways like that are pretty much the perfect gathering spot for ghosts. It's because they cut through dimensions unlike anything else.

[Just a fun fact, in case Richie was at all curious.]

Anyway, it's probably because of that that the Porta Nectere showed up there.