Town with saline thermal baths. Twain lived there with his family from June to September of 1892, although he returned alone to the States for several weeks.  The family moved to Florence, Italy at the end of September.

July 23, 1878: The Clemens family traveled by rail to Baden Baden, Germany, staying in the Hotel de France. Sam remembered the hotel as a “plain, simple, unpretending, good hotel” in chapter 21 of A Tramp Abroad. The medicinal baths in Baden Baden were probably an inducement for the move.
(DbyD)

Quaker City passengers were quarantined at Piraeus but Sam and companions snuck ashore and visited Athens at night, August 14, 1867. Mark Twain Project: Quaker City Itinerary

Intended to be a highlight of the Quaker City cruise, fear of cholera caused local officials to bar anyone from coming ashore. The passengers could only make out the Acropolis from the ship through spyglasses. That night Twain, with three others went ashore and made there way to the Acropolis and back. Two others did the same later that night and two more attempted but failed, barely avoiding arrest.

A North African seaport and at the time of Twain's visit, a french colony.  The Quaker City anchored here for five hours on October 15, 1867.  Cholera was reported so no passengers went ashore.

At the beginning of the 17th century, the Aix people and the medical world had begun to become aware of the value of the hot springs of Aix, through the writings of the dauphinois physician Jean Baptiste Cabias, who was followed in this area by other renowned doctors. Indeed, since ancient times the exploitation of sources of hot water had never been completely forgotten. Bathing took place in Aix in the Middle Ages and until the end of the 18th century, in the only existing Roman pool, outdoors, or at home where the spa water was brought by hand.

June 27, 1894 Wednesday – Frenchmen were rioting throughout the country, angry over the assassination of President Sadi Carnot on June 24. Sam wrote of a crisis situation at the Grand Hotel in La Bourboule, which had several Italians in their employ.

See letter to Rogers, June 29.

Mark Twain first visited Paris July 6, 1867 as part of his "Innocents Abroad" excursion. In late February of 1879 he returned with his family and stayed until July. "The weather was miserably cold; he suffered from rheumatism and dysentery and spent most of his time in bed." Again in June of 1891, he passed through the city returning three years later for a stay of from March until June of 1894, then from October 1894 through May of 1895. (Mark Twain A to Z)

Le Havre (/lə ˈhɑːv(rə)/, French: [lə ɑvʁ(ə)]; Norman: Lé Hâvre [lɛ ɑvʁ(é)]) is a major port city in the Seine-Maritime department in the Normandy region of northern France. It is situated on the right bank of the estuary of the river Seine on the Channel southwest of the Pays de Caux, very close to the Prime Meridian. Le Havre is the most populous commune of Upper Normandy, although the total population of the greater Le Havre conurbation is smaller than that of Rouen. After Reims, it is also the second largest subprefecture in France.