the Italian city-state of Mantua was ruled by a marquis.
Explanation:
On the occasion of his visit to Mantua, Emperor Sigismund made Marquis Gianfrancesco Gonzaga (1433) an extendable title to his heirs, not before and as usual, having given the new Marquis a large sum of money. This alliance was reinforced by the marriage of the Ludovico heir with a niece of the emperor, Barbara de Brandenburg.
