The first major city that players come across in Starfield is New Atlantis, which is on the planet Jemison in the Alpha Centauri system. The city is big and has plenty for players to do, but the planet Jemison has more to it than just one city.
Starfield: How To Complete the Survey of Jemison (All Resources, Fauna, and Flora)
Jemison is more than just the home of New Atlantis, it's a vibrant world full of life that players can survey.