Avon
Avon Avon
It used to be in Avon but it is now a City Council in its own right, however some parts are in South Gloucestershire.
Bristol is its own county, often known as City of Bristol. It was formerly in the county of Avon, but that no longer exists, despite almost every online form suggesting it does!
691 square miles, 691 square miles, 691.12 square miles and 556 square miles