At this time, Ghent was subject to the rule of the Holy Roman Emperor and Spanish king Charles V, though it was his sister, Mary of Hungary, who actually governed the region as his regent. Ghent was in the Burgundian Circle of the Holy Roman Empire. Ghent and the Low Countries in general were an international center of trade and industry and therefore an important source of revenue. Ghent had lucrative commercial ties to France. Ghent had a population of 40,000 to 50,000 people.