An AU set in another time period.
Some ideas of other times:
Victorian (Steampunk)
The Roaring 40's (Dieselpunk/ World War II/ The Great Depression)
Medieval
Wild West
Edo period, Japan
60's
Civil War (American Civil War, not Captain America Civil War)
Ancient times (Egypt, Rome, Greece etc)
Jane Austin times
You may even make this a time travel chapter if you would like.
