Rivendell during the school year and the Shire during summer break.
The Lost island for about a month after the holidays, to lose the holiday weight (but when they were eating only fish and fruit, at the beginning of the show).
The Victorian villages in either Pride & Prejudice, Emma, or Mansfield Park.
I’m sure there’s a futuristic city one also… have to think a little more. Gotham always seemed kind of depressing to me.