The whole concept of Hariharnath kshetra sonpur mela started around the worship of lord hariharnath(vishnu and shiva) for which people came to sonepur. This mela is largest cattle fair of Asia.The sonepur cattle fair is held on kartik purnima(the full moon day) in the month of november in sonepur,bihar on the confluence of river ganges and gandak.The day is supposed to be very auspicious for the worship of lord hariharnath.It is also known as hariharnath mela and it attracts visitors from all over asia.Till date it is one of the biggest cattle fairs of asia and stretches on from fifteen days to one month.It has origins from ancient times when chandragupta maurya (340-297 BCE) used to buy elephants and horses across the river ganges. Today it has become a fusion of traditonal as well as modern activities which ranges from historical snan at different ghats and visiting temples to stalls and amusement parks .It has stalls of different government departments along with showcasing local artists and cattle traders