CityVille, Zynga's most popular game and one of the most popular social games on the Web, is now available on Google+.

Quite the most popular game on Facebook, CityVille had more than 100 million dedicated users at a certain point in time. Of late, however, the game has experienced a certain drop in popularity; even so, it still clocks 70 million users. The announcement is, nevertheless, seen as a potential setback for Facebook, which admits that Zynga players account for roughly 30 percent of its most engaged users.

The game permits players to become the Mayor of a virtual city and to oversee its development into a large metropolis, allowing players to perform tasks that include farming, construction-related activity and collect rent, all of which are to be spent on energy points.

Zynga had agreed to keep its games exclusive to Facebook, in exchange for marketing support and the use of Facebook Credits. However, they then had to hand over 30 percent of their revenues to Facebook.

Google+ has approximately only 50 million users, compared to Facebook’s staggering 800 million. Nevertheless, considering the fact that Google+ is planning to grab users by all possible methods, this move is a step in the right direction for the expansion of their social network.The partnership could be strategically significant for both Google and Zynga, since they do seem to need one another.

On the one hand, Zynga needs Google+ as an alternate platform in order to achieve more independence from Facebook, while Google+ is in need of successful games like those from the Zynga stables, to attract people to its fledgling network.

As per a report by Experian Hitwise, the newly-launched social network Web site - Google+ - saw U.S. visits soar 13-fold last week, after the site opened to the general public. The network had been in field trial mode for the past 12 weeks; a fact that did not deter 10 million users from looking to sign up in that period.