Blenshaf
From Girl Genius
The Duchy of Blenshaf is one of apparently several places that produces gyro wheels[1]. The circus wagon in which Agatha identified one by its sound remained upright even though it had at most one set of wheels in a single straight line; thus, the gyro wheel referenced may have been a large flywheel which supplied gyrostabilization. Another example of a vehicle which would appear to require some such mechanism to remain upright is the Prisoner Transport seen later.
