barouche, landau:

a four wheeled carriage drawn by two horses with two benches, allowing the passengers to face each other across the middle, with a separate box for the driver, often protected by a folding cover. In Emma, Mrs. Elton speaking of her brother and sister: “They will have their barouche-landau, of course, which holds four perfectly.” I believe a landau to be similar to a barouche, probably larger and drawn by four horses. You would have seen Prince William and Princess Kate being taken back to Buckingham Palace from Westminster Abbey in one of the state landaus.