A major attraction, Bhul Bhulaiya, is a part of huge structure (Bara Imambara) in Lucknow. Bhool Bhulaiya is a labyrinth of hundreds of narrow stairway passages, some of which have dead-ends, some end at precipitous drops while others lead to entrance or exit points. One should always take a Guide to explore Bhool Bhulaiya. The Bhool Bhulaiya was constructed to confuse any enemy intruder. The narrow lanes of the labyrinth can make anyone feel lost. The king and other few only knew the way out. The Bada ImamBara is said to be the world's largest arched room without any pillars. The bhool bhualiyaa in the building is three storeyed. It is surrounded with 489 doorless similar galleries, where one can roam endlessly for hours. This is why it is so mysterious. The structure contains various strategically built hollows in the corridors. There is also a blocked passageway which, according to legends, leads through a mile-long underground passage to a location near the Gomti river. In short, it is simple in style but mysterious too.