In Japan, they raise the floor to indicate shoes must be taken off before stepping on the elevated floor. I need a word for the part of the floor that is not raised. Any suggestions?
"Sunken" might be what you are looking for, if set below the normal level of the floor.
"Flush," if at the normal level of the floor.
"Level" could work:
having no part higher than another; having a flat or even surface
foyer: "...you may hang your coats in the foyer"
NORTH AMERICAN = an entrance hall in a house or apartment..."
If you were to ask your guests to remove their shoes in the foyer, they would know that you were indicating the entrance area.
(In larger, public buildings, the North American word for this entrance space is "lobby". Though "foyer" is sometimes used instead of "lobby" when referring to larger buildings, "lobby" is never used to describe space in a home that is a single-family house or dwelling.)
Although I think "by the front door" is also commonly used to refer to this part of a house. My mother used to call this the "anteroom" - too formal and old school now - but as my son was growing up and he would bring a gang of school friends home, I would remind them to leave their shoes "by the front door" as I knew their parents similarly used that phrase.
"Recessed" is used to describe the opposite of "raised", but I think it's more design jargon than space-naming convention.