CityVille has surpassed FarmVille as the most popular application on Facebook.
About 69 million have played CityVille over the last 30 days, according to a Monday report from AppData, a website that tracks the use of Facebook applications.
FarmVille, formerly the most used app on Facebook, has been played by about 57 million people over the last month, said AppData, which collects information on more than 75,000 apps directly from Facebook.
Both CityVille and FarmVille are made by Zynga, a San Francisco-based company that also makes the fourth- and fifth-most popular Facebook apps, FrontierVille and Texas HoldEm Poker.
In CityVille, which was released just over a month ago, players create digital cities that they manage as mayor, deciding how in-game funds are spent to nurture local businesses, build infrastructure and attract residents.
Just as in FarmVille, players can visit the communities their friends create in the game and even operate businesses in their friends' cities.
Zynga has built more than 50 apps on Facebook, as well as for Yahoo, the iPhone and the former-most-popular social networking website, MySpace.
According to AppData, Zynga has a substantial lead as the most popular Facebook app company with about 271 million people having used its products over the last 30 days.
That's more than double the number of users than the second-most popular Facebook app company, Takeoff Monkey, which had about 60 million users last month, AppData reported.
Explore further: Social network game developer Zynga unveils 'CityVille'