A monstrous piece of the tower lies across the portal. It wasn't an earthquake that brought down the former watchtower, but rather a deliberate barrage of cannonballs by the Spanish occupiers during the 28-year conflict to restore Portuguese sovereignty. Serpa, a border town coveted for its mineral resources, changed its national flag several times over the course of its turbulent history along the border between the once-enemy kingdoms of Castile and Portugal. In 1674, the then Prince Regent and future King Pedro II awarded Serpa the title of Vila Notável de Serpa. Despite extensive destruction, the "remarkable town" managed to hold its ground and was awarded the honorary royal title that remains in use today.