Isaac Gewirtz, in Mark Twain A Skeptic's Progress, writes of Twain's view of the French Revolution:

On looking at the map, this location seems to actually correspond to Ayassalook, where the Quaker City party got off the train and took donkeys to Ephesus.

Ephesus was one of the great cities of the eastern Mediterranean during Roman times.  It contained the Temple of Diana which was considered one of the Seven Wonders of the World.

Near Eberbach there is a crumbling ruin known as the "Spectacular Ruin".  The raft captain tells a tale about a dragon that terrorized the region. A Sir Wissenschaft killed the dragon with a fire extinguisher and was granted a spectacles concession by the emperor for his heroism.

Source of the Jordan River. Sam and the pilgrims arrived there after about an hours ride over a rough, rocky road. September 18, 1867.  He refers to Dan as "Dutch Flat".

The territory of Crimea, previously controlled by the Crimean Khanate, was annexed by the Russian Empire on 19 April [O.S. 8 April] 1783. The period before the annexation was marked by Russian interference in Crimean affairs, a series of revolts by Crimean Tatars, and Ottoman ambivalence. The annexation began many years of Russian rule in Crimea, which ended with the transfer of the territory to the Ukrainian Soviet Socialist Republic in 1954. Russia annexed Crimea for a second time in March 2014. https://en.wikipedia.org/wiki/Annexation_of_Crimea_by_the_Russian_Empire

Known as Istanbul since 1939, Twain arrived aboard the Quaker City August 17, 1867.  The ship remained there for two days then continued into the Black Sea.  Eight fellow passengers remained in the city until the ship returned to take on coal August 29.  It remained for 5 days.  Twain was particularly impressed with the Stamboul's bazaar.

Sam and companions traveled by train from Milan to Como and then took a steamer to Bellagio on July 18th. Mark Twain Project: Quaker City Itinerary

Twain also made a day trip to Chiasso, in Switzerland, from Como.

From August 19-30, 1867 Twain sailed the Black Sea aboard the Quaker City:  From Constantinople, through the Bosporus to Sevastopol, Odessa, and Yalta.