Speer expressed his views on the matter in the Four Year Plan of 1937 in his contribution "Stone Not Iron" in which he published a photograph of the Parthenon with the subscript: "The stone buildings of antiquity demonstrate in their condition today the permanence of natural building materials." Later, after saying modern buildings rarely last more than fifty years, he continues: "The ages-old stone buildings of the Egyptians and the Romans still stand today as powerful architectural proofs of the past of great nations, buildings which are often ruins only because man's lust for destruction has made them such." Hitler approved Speer's "Law of Ruin Value" (Gr. "Ruinengesetz") after Speer had shown him a sketch of the Haupttribüne as an ivy-covered ruin. The drawing pleased Hitler but scandalised his entourage.