Who built Imambara and Rumi Darwaza?

Rumi Darwaza was built by the fourth Nawab of Lucknow, Nawab Asaf-ud-Daula and is believed to be identical to an old gate in Istanbul called Bab-i-Hümayun, and so is also sometimes referred to as Turkish Gate. The 60 feet high gate is now considered an architectural marvel, but it built for a noble purpose.