Bismarck Statue = The Argonauts.

[The Squatter of Amon Rûdh]

Tempting though it is to think that Tolkien based the pillars of the Argonath on a specific statue he had seen, I notice that Bismarck is holding a sword, with both of his hands clasped on the hilt and a shield at his feet as befits a commemorative work. The statues of Isildur and Anárion hold axes in their right hands, with their left hands extended in warning, as one would expect from a statue placed as a border marker. Other than the fact that all are large statues of armed men, I can't see that they have enough in common to suggest a direct inspiration, although I suppose that some illustrations of Tolkien may have been influenced by the German statue.