" 
 : No, you are not going to merge two different topics, even if you believe they are the same. Do you want to add a photo of the building to the article written by Piotrus? Preußischer Landtag covers several meanings over several centuries, up to the present day building. The current English article may be a mere stub in need of expansion and clarification, but thats no reason to redirect it to the article Prussian estates, which according to its content only covers the pre 1772 period in the Monastic state and Royal Prussia. It should be moved to Royal Prussian estates, and focus about the relation with the Polish Kingdom 1466-1772, to which Polish editors should be able to contribute.     "