The city of Vienna was essentially founded by the ancient Romans, who erected several military camps along the river Danube, which was then the border of their empire. One of them, called Vindobona, lies beneath the modern city center and you can actually visit Roman excavations today. The city’s importance grew rapidly with the rise of the Habsburg empire, who made it their residence in the late middle ages. In 1529 and 1683, Vienna was sieged by Ottoman armies, but they failed to conquer the city in both cases.
And therefore it is not at all surprising that she is so rich in this regard)