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kilometer or so west of the Residency are the two fascinating Imambaras. In 1784, Asaf-ud-Daula built the Bara Imambara. The great vaulted hall (open 6 am - 5 pm), reputedly the largest room in the world, is 50 meters (165 feet) long and its 15-meter (50 foot) high roof is unsupported by pillars. The hall, the great mosque and its two supporting minarets were built as part of a famine relief project. Most of the underground passages are now blocked, but an external stairway leads to the labyrinth on the upper floor known as the Bhulbhulaiya. In front of the Imambara is an impressive gateway, Rumi Darwaza, built in imitation of Istanbul\'s Sublime Porte. Beyond the gateway, the Husainabad Imambara stands in a large quadrangle in front of an inlaid marble tank. The main building (open 6 am-5 pm) contains the silver throne of the nawabs.