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.
it’s a bit hard to tell. of the buildings still standing and in use, the cathedral comes to mind, with was consecrated in 1238, but it stands on the site of the old mosque. this was torn down apparently in 1262, at which point construction on the cathedral began, but it would take centuries to finish everything.
there is another church that was named a parish in 1245 and so was probably already standing then, so perhaps that building is the oldest? I don’t knoe how much of that original building is still standing though