Hariharnath Mandir (हरिहर नाथ मंदिर) in Sonepur is also known for the famous temple of shree Hariharnath and the site of the battle of Gaj-Grah and rescue of the former by Hari During Kartik Purnima Ganga Snan or ceremonial bathing in the Ganges is held by Hindus to be unusually efficacious. On the day of full moon (Kartik Purnima) immense crowd assembles and take bath. The Mela commences on that day and lasts for more than a fortnight. The Shiva temple, Kali temple and other temples and historical religious monuments are situated here and social and economical activities are at the highest peak during the Mela period. People come here to pay their oblation to the lords and thus its importance is not within Sonepur of Bihar rather it is of India and world fame.

According to Uday Pratap Singh, author of the book Baba Hariharanath, before 1757, the Hariharanath temple was composed of artistic rock clusters of timber and black stones. These pictures and praises of Hari were engraved on them. Meanwhile, this temple was reconstructed by Ram Narayan Singh, the deputy sub-ruler of Mir Qasim. He was a resident of Nayagaon, Saran. After this, in 1860, the Empress of Tekai built a hospice in the temple premises. In 1871, the remaining three oases of the temple complex were constructed by Maharana Jangbahadur of Nepal. In the 1934 Nepal–Bihar earthquake, the temple complex, Osara and Pakora were damaged. After this Birla family rebuilt it. English writer Harry Abbott has highlighted the importance of this temple in his diary while visiting the Harihar Nath Temple. In 1871, English writer Minden Wilson described the Sonpur fair in his diary.

Hariharnath Mandir :
Hariharnath Mandir in Sonpur is also known for the famous temple of shree Hariharnath and the site of the battle of Gaj-Grah and rescue of the former by Hari During Kartik Purnima Ganga Snan or ceremonial bathing in the Ganges is held by Hindus to be unusually efficacious. On the day of full moon (Kartik Purnima) immense crowd assembles and take bath. The Mela commences on that day and lasts for more than a fortnight. The Shiva temple, Kali temple and other temples and historical religious monuments are situated here and social and economical activities are at the highest peak during the Mela period. People come here to pay their oblation to the lords and thus its importance is not within Sonpur of Bihar rather it is of India and world fame.

Baba Hariharnath:
An ancient and great temple of Lord Siva and Lord Vishnu.This temple is made in the holy area 'Hariharkshetra' where a great animal fair named 'Sonpur fair' or 'Hariharshetra fair' gets organised every year in the Hindi month of 'Kartika'. It is believed that the temple of Harihar Nath was built by Lord Rama on his way to court of King Janak to win the hand of Mata Sita and later repaired by Raja Man Singh. Finally Raja Ram Narain further modified the temple during the late Mughal period. These days, Sonpur fair also called Harihar Kshetra Mela is administered by District of Chapra with support from Bihar Govt. and promoted by the Tourism Ministry of Bihar. The administration also arranges health and welfare camps, sanitation, drinking water facilities for the visitors.

History, story of Harihar nath temple in Bihar:
History and story of Harihar nath temple in sonepur Bihar can be found here. Harihar Nath temple in Bihar was built by Lord Rama, while going in the swayambar of Sita Mata. People perform puja at harihar nath temple when to come to sonepur mela and take dip in holy rive at the meeting place of ganga and Gandak.

Story, legend Gajendhra Moksha and Harihar nath temple:
You might have heard the story of Gajendhra Moksha, in your childhood days. If you have not here is the Gajendhra Moksha story. As per the legend of Gajendhra Moksha, king Indrayamuna and the Gandharva chief Huhu, were turned into an elephant and a crocodile respectively by sages Agasthya and Dewala muni. One day the elephant's leg was caught by the crocodile. The elephant tried to free himself of the hold for many years but could not do so. Finally he prayed to Lord Vishnu to save him. Lord Vishnu freed the elephant from crocodile hold by cutting him with his Chakra. At that time both of them were also released from the curse of the sage and Lord Vishnu took the gajendra with himself to vaikuntha.

How To Reach

RoadWays:
Sonpur is nearly 3 Km from Hajipur and 25 km from Patna and 58 km from Muzaffarpur in Bihar & 60 km from Chhapra, the headquarter of Saran District. Buses, Taxis and Auto-rickshaws are easily available.

Railways
Sonpur station The Nearest Railway Station is Sonpur Junction railway station. It has the 8th Largest Railway Platform in the World. It has trains connecting almost every part of India. It is the divisional headquarters of the East Central Railway of the Indian Railways.

Waterways
BSTDC organizes ferries to Sonpur during the Season of Sonpur Cattle Fair.