Complex sentence: Ghumdan Palace tower, a 20-storey high rise building, is believed by many to have been the world's earliest skyscraper, and it was considered to be one of the thirty wonders of the ancient world.
Split into simpler sentences: Ghumdan Palace tower, a 20-storey high rise building, is believed by some to have been the world's earliest skyscraper. Ghumdan is believed by many to have been the world's first skyscraper and it was considered to be one of the thirty wonders of the ancient world.