One thing that my Lyriaverse has in common with the Potterverse is dimensional expansion, IE "bigger on the inside" magical tech. And it occurred to me, from a line in HP5 about there not being enough beds in Hogsmeade to accommodate all the people staying for Dumbledore's funeral, that it was kind of odd that there should be such a shortage. I mean, with the right magic, an inn the size of a small shack on the outside could conceivably hold, say, 50 rooms.
So an idea came to mind for the Lyriaverse, of inns that are only 2 or 3 stories tall, and less than a city block in size, but which have hundreds of rooms inside.
Granted, there are still limits, and the larger something is inside, the more problematic getting out in an emergency becomes. Things like Lyria's fortress are quite rare, Lyria being the only known mortal to know how to make a Fae style Knowe, so once a building was expanded on the inside, that would be that; it would not be able to expand any more or less, unlike Lyria's fortress.
Plus, I imagine it would take a very well educated and highly skilled mage to make such a dimensionally-expanded area. So far, the only building in Lyriaverse canon to have such expansion (aside from Lyria's fortress) is one of the Way Stations - takes up a whole city block on the outside, is at least three times bigger on the inside to accomodate all the hundreds of permanent portals to various locations.
So I guess that explains the shortage, if the same kind of thing is true in the Potterverse. But I still like the idea of one of the wealthier inn owners making an inn much bigger on the inside. Even if it was simply taking an inn with rooms only a square foot or two in floor surface area and expanding their insides to be, say, 10, 15, or more square feet in floor area.
Update: I've decided that there are limitations regarding dimensional expansion, for people who don't know how to make a Fae style Knowe. So I decided the best option would be to first build a building that has lots of small rooms, each with their own door, then each room expanded.
As Brooke pointed out, there could be issues if the spell fails. Unlikely, because the laws would recognize the danger and there'd be multiple backups of the spell, an emergency ejection spell, an emergency portal in case that fails, and spells to reinforce the building in case of emergency. (And anti-fire spells.) I figure if the king takes the safety of his people strongly enough, they can do some really powerful stuff. After all, there IS a small town on the edge of the supercontinent of Taanshibaar, that is almost continually battered by hurricanes and mega-hurricanes called hypercanes. This town, called Port Insanity, is made entirely of wood but almost never has to be rebuilt because the buildings can withstand winds up to 600 MPH. (Its people are all mages; they need to be to cast spells to keep them from being blown away by the winds of the storms, and to keep debris like leaves and wood slivers from injuring or even killing them.)