By @waddled
Apartment 305 is a roomates!HoO AU. It’s one of my absolute favourite HoO fanfics, because it’s just mwah, the plot and the characterisation is so good!
Annabeth and Piper are roommates, and one evening when they order pizza a certain black-haired guy comes to deliver the wrong one, and it all spirals from there. There’s an immense depth of worldbuilding, and everyone and their mother from the canon is pulled in, and in interesting ways! Percy is an Olympic swimmer, Jason is an unwilling heir to his manipulative father’s empire, etc. etc.
I did get lucky because I read it while it was being written, right from the get-go, and reading it now might be hard because it’s like 600k+ words. Very good though.