15 Incredible Hannibal Sites To Visit This Summer Over the weekend while I was at Twain on Main, I was not only taken back by all of the people who showed up, but also reminded on how lucky we are to have Hannibal in the Tri-States. I think we take for granted the incredible sites and historical places to visit in Hannibal, because well we can go and do those things anytime. Well, I am making it a mission this summer to see all of these 15 sites to visit in Hannibal (and you should too). Everything from Mark Twain's Boyhood Home, to the Mark Twain Cave, and Rockcliffe Mansion, there really is something magical about spending the afternoon in Hannibal.