Leviticus 25:30-31

30If it is not redeemed by the end of a full year, then the house in the walled city is permanently transferred to its purchaser throughout his generations. It is not to be released on the Jubilee.

31But houses in settlements that have no walls around them are to be classified as open fields. The right to redeem such houses stays in effect, and they are to be released at the Jubilee.