History
Sky City is a floating city created by Amadeus Cho to act as a refuge for the citizens of Sakaar. Movement to and from the city was done using flying vessels. When more energy was required to keep the city afloat, Cho was in hiding and couldn't be found to help. So, Jen Walters offer to turn herself into a gamma battery to keep the city afloat and did so for the next 83 years.
One day, Cho returned with his granddaughter Tala to seek Jen's help in rescuing Haarg children being held prisoner by the Grand Priestess Venkiera. Jen agreed and disconnected herself from Sky City, causing it to plummet. The city safely landed in a river, turning it into an island.[1]