Complex sentence: To service the building the Great Northern Viaduct was built parallel to the Cornbrook viaduct over the basin, and over Kenworthys Warehouse, and to mask it from Deansgate was the country's longest Victorian commercial terrace.
Split into simpler sentences: To service the building the Great Northern Viaduct was built parallel to the Cornbrook viaduct over the basin, and over Kenworthys Warehouse. To mask it from Deansgate was the country's longest Victorian commercial terrace.