I think the answer is "Having seen the Statue of Liberty, the Grand Canyon is more impressive." The Grand Canyon has not seen the Statue of Liberty; you have, but you- or "I" - are nowhere in the sentence. To correct the sentence, it would need to read something like this: Having seen the Statue of Liberty, I find the Grand Canyon more impressive.
You didn't provide us with the text.
Twain accomplishes his purpose chiefly through telling a story within a story, also called a "frame story".
