Isabella I was Queen of Castile from 1474 until 1504. Together with her husband, Ferdinand II of Aragon, these Catholic Monarchs unified Spain and launched the Age of Exploration by funding the first voyage of Christopher Columbus. In 1502, they passed a Royal Warrant establishing this escutcheon as the coat of arms of Gibraltar. The three castles represent Castile. The key symbolizes Gibraltar’s position as the entrance to the Mediterranean Sea. This is the oldest coat of arms of all British Overseas Territories.