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.
Must be the church St. Pancratius, built somewhere between 1100 and 1120.
The second-oldest building here is probably the remains of the castle of the poem “The castled crag of Drachenfels” by Lord Byron.