Bara Imambara was built by Asaf-ud-Daula, Nawab of Awadh, in 1784. It is also called the Asafi Imambara. It was built as a part of a relief project for a major famine that took place in the year 1784.
The Great Imambara is classified as Nawabi architecture -this last phase of Mughal architecture -indicating the demise of an empire and its cultural product. Nawabi architecture is divided into two phases: the first towards the end of the eighteenth century is characterized by grandiose and stylistic buildings; the second in the nineteenth century is distinguished by the incorporation of European elements.
The Great Imambara created in the first period of Nawabi architecture, is one of the few buildings in Lucknow devoid of European elements
The complex comprises two stepped gardens with tall gateways and a series of arched doorways (ghulam gardish) in the boundary. The step well (baoli) is more characteristic of Hindu than Muslim architecture but integrates with the Imambara and mosque to create a ‘paradise garden’ quality.
It has a big mosque known as the Asafi masjid. Shia muslims gather there to offer prayers every Friday and also hold the annual namaaz on the occasion of Eid and Bakrid.
Source
http://www.gardenvisit.com/gardens/bara_imambara%20%20
http://lucknow.me/Bada-Imambara.html