Complex sentence: However, the majority of Sheffield's older buildings were built during the Industrial Revolution, with a large number of Sheffield's medieval buildings demolished in the 19th century; some older buildings were also lost during the Sheffield Blitz.
Split into simpler sentences: However, the majority of Sheffield's older buildings were built during the Industrial Revolution. Many of Sheffield's medieval buildings were demolished in the 19th century, and some older buildings were also lost during the Sheffield Blitz.