April 25, 1878: Thursday – The Clemens family arrived at Hamburg and took rooms at the Crown Prince Hotel. Sam insisted that the family rest in Hamburg a week. They stayed five days. Livy wrote her mother on Apr. 26 that Hamburg “was the finest city I was ever in”.

Twain, in a letter to William Dean Howell, describes his journey from Hamburg to Heidelberg as "...fooling along, 4 hours per day by rail, with a courier, spending the other 20 in hotels whose enormous bedchambers & private parlors are an overpowering marvel to me." He is not particularly detailed about his itinerary, however. The letter was posted from Frankfurt on the Main, 4 May 1878, near the end of the journey.

The Clemens party took rooms at the Hotel Schloss in Heidelberg from May 6 to July 23 of 1878.

From Chapter 2 of A Tramp Abroad: At Heidelberg

The Clemens party left Heidelberg on 23 July 1878 and proceeded to Baden-Baden, where they would meet Joe Twichell on 1 August.

Twain hired the portier of the Schloss Hotel, Georg Burk, as courier for $55/month and expenses and departed Heildelberg by train for Baden.

There are two possible railway lines that could have been used for this trip:

August 12 Monday – The men left Baden Baden by rail and arrived at Lucerne, Switzerland where they joined Livy, the children and the rest of the party who had been there a few days.

The German railway, Mannheim-Karlsruhe-Basel railway, and the Swiss, Swiss Central Railway.

February 27 Thursday – The Clemens family left Munich by rail for Paris, France. Sam had planned to leave at 6:40 AM and travel to Strasburg (at that time in Germany) by 5:30 PM and spend the night there, continuing on to Paris on Feb. 28 [MTLE 4: 29]. Sam noted “Feb 27, at Strasburg” in his notebook [2: 292].

From Munich to Ulm:  The Bavarian Maximilian’s Railway. From Ulm to Stuttgard. Karlsruhe and Strassburg:  Royal Württemberg State Railways