Complex sentence: The Islamabad Rawalpindi metropolitan area is Pakistan's third most populous metropolitan area, it consist's principally of the twin cities of Islamabad and Rawalpindi along with smaller town's of Murree, Wah Cantonment and Taxila, and several suburb's including Bahria Town and Bani Gala.
Split into simpler sentences: The Islamabad Rawalpindi metropolitan area is Pakistan's third most populous metropolitan area. It consist's principally of the twin cities of Islamabad and Rawalpindi along with smaller town's of Murree, Wah Cantonment and Taxila, and several suburb's including Bahria Town and Bani Gala.