Gajendra Moksha गजेन्द्रमोक्षः

शुक्लांबरधरं विष्णुं शशि वर्णं चतुर्भुजं । 
प्रसन्न वदनं ध्यायेत सर्व विघ्नोपशान्तये॥ 
Gajendra Moksha गजेन्द्रमोक्षः or The Liberation of Gajendra is Puranic legend from the 8th Skandha of Bhagavad Purana, one of the most sacred books in Hinduism. It is one of the famous exploits of Lord Vishnu. In this moving episode Lord Vishnu came down to earth to protect Gajendra, the Elephant from the clutches of Makara, the Crocodile and awards him moksha or salvation. Gajendra is then said to have attained the similar four-armed form (Sarupya Mukti) of God and goes to Vaikuntha with Lord Vishnu. 

Gajendra Moxa Gujarati Path
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There was once an elephant named Gajendra who used to live in a garden called Rtumata which was created by Varuna. This garden was situated in the beautiful mountains of Trikuta in ancient India. Gajendra ruled over all the other elephants in the herd. On a hot day, he proceeded with his herd to a lake to cool off in its fresh waters. Suddenly a crocodile living in the lake attacked Gajendra and caught him by the leg. Gajendra tried for a long time to escape from the crocodile's clutches. All his family, relatives and friends gathered around to help him, but in vain. The crocodile wouldn't simply let go. When they realised that ‘death’ has come close to Gajendra, they left him alone. He trumpeted in pain and helplessness until he was hoarse. As the struggle was seemingly endless and when the last drop of energy was also sapped, Gajendra called to god Vishnu to save him, holding a lotus up in the air as an offering. It is believed that Gajendra's foot was held by the crocodile for over a thousand of years. Hearing his devotee's call and a prayer, Lord Vishnu rushed to the scene. As Gajendra sighted the Lord coming, he lifted a lotus with his trunk, seeing this lord was pleased and with his Sudharshana Chakra separated the crocodile's head from its body and Gajendra prostrated before the Lord. Vishnu informed Gajendra that he, in one of his previous births, was the celebrated King Indradyumna, a Vishnu devotee, but due to his disrespect to the great Sage Agastya, he was cursed and had to undergo this life. Because Indradyumna was a chosen one, Lord Vishnu had him born as Gajendra and made him realize that there is something called, "Kaivalya" which is beyond Svarga and Urdhva Loka. Indradyumna could attain Moksha finally when he (as Gajendra) left all his pride and doubt and totally surrendered himself to Vishnu. The prayer made by Gajendra on this occasion became a famous hymn in praise of Vishnu called the Gajendra Stuti. 
it is believed that this incident has happened in Sonepur. There is a Temple Devoted to Lord Vishnu known as "Hariharnath Mandir" at the banks of Gandaki River. Sonepur hosts one of the world's largest cattle fairs in Asia which starts on Karthik Poornima. Sonepur also has the confluence of four rivers.