The Bada Imambara was built by Asaf-ud-Daula, the Nawab of Lucknow, in 1784. Often referred to as Asafi Imambara, it is a shrine built by Shia Muslims for the purpose of Azadari.Classified as Nawabi architecture, the edifice is part of the Asaf-ud-Daula Imambara Complex that contains a mosque, courtyards, gateways and a 'bawali' or step-well that was used as a summer palace. Built as part of a famine relief program following the famine, the complex is one of the earlier attempts in Lucknow to imitate a Mughal complex.One of the few buildings in Lucknow devoid of European elements, the edifice incorporated high-arcaded battlements even when security was not a concern. The main hall can be reached by two gateways.Asfi mosque, the Bhool Bhulaiyaa (the labyrinth), and bowli, a step well-with running water are some of the structures that together make up the complex. According to legends, the edifice also contains a blocked (tunnel) passageway, which leads through a mile-long underground passage to a location near the Gomti River.After a period of long disuse, other passages, including the ones rumoured to lead to Faizabad, Allahabad and Delhi have been sealed. A maturation of ornamented Mughal design, namely the Badshahi Mosque is reflected by the architecture of the complex.It is one of the last major projects not incorporating any European elements or using iron. A large vaulted central chamber containing the tomb of Asaf-ud-Daula is located within the main imambara.Counted among the largest such arched constructions in the world, it is spread over an area of 800 square metres and is over 15 metres tall. Containing no beams supporting the ceiling, it has eight surrounding chambers built to different roof heights.This has permitted the space above these to be reconstructed as a three-dimensional labyrinth with passages interconnecting each other through 489 identical doorways. Bhool Bhulaiyaa is formed by the many balconies and passages that branch off from 489 identical doorways.