Complex sentence: The old city of Petra was the capital of the Byzantine province of Palaestina III, many churches were excavated in and around Petra from the Byzantine era, in one of them more than 150 papyri were discovered which contain mainly contracts.
Split into simpler sentences: The old city of Petra was the capital of the Byzantine province of Palaestina IIIand many churches were excavated in and around Petra from the Byzantine era. In one of them more than 150 papyri were discovered which contained mainly contracts.