Birgu is a very old locality with its origins reaching back to medieval times. Prior to the establishment of Valletta as capital and main city of Malta, military powers that wanted to rule the Maltese islands would need to obtain control of Birgu due to its significant position in the Grand Harbour. In fact, it served as the base of the Order of Saint John and "de facto" capital city of Malta from 1530 to 1571. Birgu is well known for its vital role in the Great Siege of Malta of 1565.