Complex sentence: The Blake Dean Railway was an approximalely 5.5 miles (9 km) long narrow gauge railway with a gauge of 3 feet (914 mm) in the Hardcastle Crags Valley from Heptonstall to the dam construction sites near Walshaw Dean in West Yorkshire.
Split into simpler sentences: The Blake Dean Railway was an approximalely 5.5 miles (9 km) long narrow gauge railway with a gauge of 3 feet (914 mm) in the Hardcastle Crags Valley. It went from Heptonstall to the dam construction sites near Walshaw Dean in West Yorkshire.