Kumar unveiled the model of the 'Virat Ramayan Mandir" jointly with Shankaracharya of Dwarka in Gujarat Swaroopa Nand Saraswati Maharaj here.
The temple would come up at Kesaria in East Champaran district of Bihar.
Chairman of Religious Trust Board Kishore Kunal gave details of the temple saying it would be 2,800 feet long, 1,400 feet broad and 405 feet high.
The temple will be built at a cost estimated in between Rs 300 crore to Rs 500 crore, he said.
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Addressing the function, the CM said that people of Cambodia had objected to use of their name hence the temple was nomenclature as 'Virat Ramayan Mandir'.
He said the state has rich ancient historical sites.
"By carrying excavation of such sites if not gold but even more valuable heritage sites could be found in the state," he said referring to Archaeological Survey of India carrying digging at a monument in Uttar Pradesh in search of gold.
Speaking on the occasion, Shankaracharya asked people to donate one fifth of their income for religious work.
Kumar also touched Ayodhya issue and said the dispute could be resolved either through court order or mutual love and respect of the two communities.
"Hatdharmi (stubbornness) could not solve a problem...The dispute can be resolved either through court order or mutual love and respect of the two communities," he added.
Dwarka Sankracharya made light of Modi building world's tallest statue of liberty and praised Kumar for constructing world's biggest temple.