Johannesburg is the largest city in South Africa.
Bobbi Morse's Honeymoon
The Avengers soon went to South Africa to keep Ultron from getting vibranium. As the others were fighting Ultron, Bruce Banner remained in the Quinjet. Wanda Maximoff found Banner and forced him to turn into Hulk using her mental manipulation powers. Under her control, Hulk started destroying the city of Johannesburg. Iron Man donned his Hulkbuster armor in response and fought with Hulk, trying to get him to stop. Eventually, the battle ended, but the damage it caused was severe. The Avengers regrouped, forced into hiding.
Johannesburg was among the cities noted by WHiH News anchor Christine Everhart to be still "on the mend" as a result of the incidents involving the Avengers, in part due to their tactical response, as late as May 3, 2016 when the issue of the Avengers' management and responsibility was being discussed.