What is Santanni?

An outer world located across the Milky Way Galaxy from Trantor, Santanni has an Imperial University that late in the novel hires Raych Seldon. Raych, his wife and younger daughter go to Santanni. When civil war breaks out, Raych puts Manella and Bellis on a flight to Anacreon aboard the Arcadia VII, which mysteriously never reaches its destination. Raych dies heroically defending the Library.