What is an important city of the Ganga valley?

Haridwar, Kanpur, Jajmau, Allahabad, Varanasi, Mirzapur, Ghazipur, Patna, Rishikesh, Munger, Bhagalpur, Baharampur, Kolkata, Bijnor

These are the cities in Ganga Valley... If you are looking for one important place, then I think it may be Kolkata..