The old Nizamat Imambara was built by Nawab Siraj ud-Daulah in the Nizamat Fort Area. He bought bricks and mortar and laid the foundation of the building with his own hands. The old Imambara caught fire for the first time in 1842 and was partly destroyed. But it was destroyed by a fire on December 23, 1846. That day, the Nawabs and the Europeans threw a party to celebrate the weaning ceremony of five-year-old Hassan Ali Mirza. But, unfortunately, the Imambara caught fire at midnight due to the fireworks left off, and nothing survived except the old Madina Mosque. The new Imambara was built in 1847 by Nawab Nazim Mansur Ali Khan under the supervision and direction of Sadeq Ali Khan just opposite the Hazarduari Palace at the cost of more than ? six lacs. The main entrance just parallel to the north face of the Hazarduari Palace faces south. The masons took only 11 months to finish the construction in addition to their wages. They also received food which allowed them to work day and night. The present Imambara is 680 feet long. However, the breadths vary. The central block that has the Madina is 300 feet long. The old Madina Mosque still stands between the new Imambara and the Hazarduari Palace near the Bacchawali Tope and the Clock Tower of Murshidabad. The present Imambara has been divided into three large quadrangles as follows: The central quadrangle has the Madina Mosque and the Memberdalan. The eastern quadrangle has the Naubat Khana. The western quadrangle has a two-storied Mosque. The mosque stands on the Mint Ghat and rises almost from the Bhagirathi River as the distance may be a few feet.
