The correct answer is Lucknow.

• Lucknow is situated on the bank of Gomati River. 
• Lucknow is the capital city of Uttar Pradesh.
• Gomati River is the tributary of the river Ganga, originates from Gomat Taal in the Pilibhit district of Uttar Pradesh.
• It is the only tributary of Ganga which originates from land.

• Ganga is longest river of India, about 2500 km long.
• River Ganga is declared as Nation River of India by Government of India in 2008.
• The confluence of Bhagirathi and Alaknanda at Devprayag in Uttarkhand is said to be the upper phase of Ganga.
• Bhagirathi originates from Gangotri glacier at Gomukh and Alaknanda originates from Santopath glacier.
• Although Alaknanda is longer than Bhagirathi, instead of that Gangotri is considered to be the origin of River Ganga.
• Ganga is considered to be the most sacred river by Hindus.
• The self purification property of river Ganga is due to the presence of a virus know as Bacteriophage.

•  Patna, Prayagraj, and Kanpur is situated on the bank of river Ganga.