When in Rome. . . .

Where did the saying: “When in Rome, do as the Romans do” come from? its clever i guess and tells people that there are certain expectations of their behaviour in many situations, but why not : when is christiania, so as the christianians do ?

It’s a generic term. Fits all situations of that ilk.

From the Phrase Finder http://phrases.shu.ac.uk/

WHEN IN ROME, DO AS THE ROMANS DO – “Don’t set your own rules when you are someone’s guest. The proverb has been traced back to the 1530 ‘Commonplace Book’ and it is first cited in the United States in ‘Voyages of Radisson’ (1885). The proverb is often attributed to Saint Ambrose (c.340-397), whose advice to Saint Augustine read: Si fueris Romae, Romano vivito more; si fueris alibi, vivito sicut ibi (‘When you are in Rome live in the Roman style; when you are elsewhere live as they live elsewhere’) English diviine Jeremy Taylor (1613-67) also used the proverb…” From “Random House Dictionary of Popular Proverbs and Sayings” by Gregory Y. Titelman (Random House, New York, 1996).

I have a little different version, after visiting in Italy.

When in Rome, drive as the Romans do.

It is different, but we could learn from them.