Complex sentence: He immediately arrived in Rome, where his election had been welcomed because he was a leading aristocrat of the Eternal City, and took up residence at the family estate on the Aventine Hill, next to the Church of Santa Sabina.
Split into simpler sentences: He immediately arrived in Rome, where his election had been welcomed because he was a leading aristocrat of the Eternal City. He took up residence at the family estate on the Aventine Hill, next to the Church of Santa Sabina.