Schloss-Hotel Heidelberg
Chapter 2 of Mark Twain's A Tramp Abroad features a full-page illustration of the Schloss-Hotel, situated high above the Neckar River. In her discussion of the illustrations in the book, Beverly R. David speculates that the picture might have been drawn by a Hartford artist working from a postcard or an advertisement in the possession of the Clemens family.
Beverly R. David. Mark Twain and His Illustrators (1875-1883). Vol. 2 of 2 vols. Troy, N.Y.: Whitston Pub. Co, 2001: 80.