At the end of the poem, the duke points out a particular statue that he keeps within the same gallery in which he retains the portrait of his last duchess. The statue depicts Neptune, the Roman god of the sea, taming a seahorse. The statue, evidently, was created by a famous sculptor named Claus of Innsbruck. It is telling of the duke's personality that he points out the famous artist who created the sculpture, just as he points out the famous artist who painted the portrait of his last duchess. He seems to appreciate prestige and ownership more than the beauty of the thing or person itself.

The subject of the statue is notable in that it depicts a great and powerful god "taming" a relatively powerless animal that lives in the waters of the ocean, just as the duke is a powerful man who can direct the people around him to do his will with his "commands." He is used to people obeying him and deferring to him, as though he were a god, and he even seems to play God by apparently deciding to have his last duchess killed so that he can marry a wife who pleases him better. He has turned his last duchess into a possession, something he can control when he could not while she was alive, by pulling the curtain on her smile so that she only smiles now when he allows it. He has "tamed" her, so to speak.