Rome was not Built in a Day
Achievements of great pith and moment are not accomplished without patient perseverance and a considerable interval of time. The French say, “Grand bien ne vient pas en peu d'heures,” but the English proverb is to be found in the French also: “Rome n'a pasété faite en un jour.” (1615.)
Rome was not built in a day, like Anchiale, of Cilicia, where Sardanapalus was buried. It is said that Anchiale was actually built in a day.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894