During the sixteenth century, many new walled cities were established along the border between France and the Spanish Netherlands. These cities were the product of a military context that needed new technical solutions (such as the bastion), and of a new classical ideal of aesthetics developed in Italy. With the cities of Hesdin, Philippeville and Charlemont as an example, this article explains how these new practices arriving from Italy were applied in the northern part of Europe. These cities, being the result of both military and aesthetic considerations, are very interesting because their urban planning had to combine a theoretical ideal with practical imperatives.