Twain and Joseph Twichell joined Twain's family in Lucerne August 12, 1878. They stayed at the Schweitzerhof Hotel until August 21. Twain returned to Lucerne in August of 1897. (See Baden to Lucerne)
From Page 260-1 The Life of Mark Twain - The Middle Years 1871-1891:
Sam soon discovered that the beauty of Lake Lucerne “had not been exaggerated,” The city, moreover, was ‘a charming place. It begins at the water's edge, with a fringe of hotels, and scrambles up and spreads itself over two or three sharp hills in a crowded, disorderly, but picturesque way, offering to the eye a heaped-up confusion of red roofs, quaint gables, dormer windows, toothpick steeples, with here and there a bit of ancient embattled wall bending itself over the ridges, worm-fashion, and here and there an old square tower of heavy masonry.” The day after their reunion, the entire family and Rosina enjoyed, as Livy put it, “a little ride on the lake" in a steamboat to Flüelen and "a most enjoyable afternoon."