Twain writes of Going to a town called Annunciation prior to his climbing Mt. Vesuvius. Torre Annunziata is the only locale I can find nearby Naples that fit his description.

Torre Annunziata is a city and comune in the province of Naples, region of Campania in Italy. It is located on the Gulf of Naples at the foot of Mt. Vesuvius.
https://en.wikipedia.org/wiki/Torre_Annunziata

In other towns in Italy the people lie around quietly and wait for you to ask them a question or do some overt act that can be charged for--but in Annunciation they have lost even that fragment of delicacy; they seize a lady’s shawl from a chair and hand it to her and charge a penny; they open a carriage door, and charge for it--shut it when you get out, and charge for it; they help you to take off a duster--two cents; brush your clothes and make them worse than they were before--two cents; smile upon you--two cents; bow, with a lick-spittle smirk, hat in hand--two cents; they volunteer all information, such as that the mules will arrive presently--two cents--warm day, sir--two cents--take you four hours to make the ascent--two cents. And so they go. They crowd you--infest you--swarm about you, and sweat and smell offensively, and look sneaking and mean, and obsequious. There is no office too degrading for them to perform, for money. I have had no opportunity to find out any thing about the upper classes by my own observation, but from what I hear said about them I judge that what they lack in one or two of the bad traits the canaille have, they make up in one or two others that are worse. How the people beg!--many of them very well dressed, too.