Complex sentence: The Mellor Mill was a huge brick structure six storeys high and 400 feet long, the River Goyt was diverted, three millponds constructed and a system of tunnels, channels and wheelpits built.
Split into simpler sentences: The Mellor Mill was a huge brick structure six storeys high and 400 feet long. As part of its construction the River Goyt was diverted, three millponds were created and a system of tunnels, channels and wheelpits built.