Roman ruins at Michaelerplatz - Founded around 500 BC, Vienna was originally a Celtic settlement. In 15 BC, Vienna became a Roman frontier city (Vindobona) guarding the Roman Empire against Germanic tribes to the north. Vienna came under threat from the Mongolian Empire that stretched over much of present day Russia and China in the 1200s. However, due to the death of its leader Ogedei Khan, the Mongolian armies receded from the European frontier and were not to return. During the Middle Ages, Vienna was home to the Babenberg Dynasty and in 1440 AD became residence city of the Habsburg dynasties from where Vienna eventually grew to become the capital of the Holy Roman Empire and a cultural centre for arts and science, music and fine cuisine. In the 16th and 17th centuries, the Ottoman armies were stopped twice outside Vienna (see Siege of Vienna, 1529 and Battle of Vienna, 1683).