A luxurious (to medieval standards, that is) travel coach.  It has
a lot of space inside, to make a comfortable journey possible
(eventhough shock dampers were not invented yet).
And plenty of bagage can be taken along, for the distant travels for
which this coach is much suited.  Believe it or not, but i actually
got my inspiration (and some parts) for this model from set 6018
(the Black Falcons Battle Dragon boat).