To those from the Western hemisphere, it’s always fascinating to hear that some homes and businesses from the times of the Greek philosophers still have inhabitants, and then you remember that the Western hemisphere is itself not without its own examples, for example some Mexican villages still have temples from the times of the Mayans.
The oldest building in/around Vienna is believed to be the Roman stone quarry in Leithaprodersdorf. It dates back to the Roman era, around 43 AD.
The oldest continuously inhabited building in Vienna is generally considered to be the Griechenbeisl, a historic restaurant located in the Innere Stadt district. It has been in operation since the 15th century.