The 28-year-old penned a four-year deal with the big-spending club on Wednesday to follow Togolese striker Emmanuel Adebayor to the Eastlands.
"It is always difficult to leave a place where you have spent the last eight years and had good times but I felt the time was right for a new challenge," Toure told City's official website.
"I am still at an age, 28, where I feel I am at my peak and will play my best football.
"For me it was time to move but only for the right club and I feel that Manchester City is that club. The ambition here is clear to see and is big. Everyone knows this club is moving and that is really, really important."
City, who are bankrolled by Abu Dhabi United Group, are strengthening their squad to book a top-four spot in the Premiership and play in the lucrative Champions League.
They have already signed Argentinean striker Carlos Tevez, Paraguay frontman Roque Santa Cruz, midfielder Gareth Barry and Adebayor.