A Hindu trust has started a 10-year project to build a replica of Cambodia's Angkor Wat temple on the banks of the Ganga.
A foundation-laying ceremony was held on Monday at the 40-acre site in Bihar where the trust plans to recreate the temple's huge structure and elaborate stone carvings.
Organisers say they intend the new building to be the tallest Hindu temple in the world.
The UNESCO-listed site in Cambodia contains the remains of various capitals from the Khmer empire and is a major international tourist destination.
The main temple was first dedicated to lord Vishnu when it was built in the 12th century before later being used for Buddhist worship.
"It will be a replica of Angkor Wat but the temple will be slightly taller than the original," Kishore Kunal, secretary of the Bihar Mahavir Mandir Trust, told AFP by telephone.
Kunal said the plan was to "recreate Angkor Wat's grandeur and splendour" near the town of Hajipur, 25 kilometres from Patna.
The trust, which has constructed a number of temples and hospitals in Bihar, is mainly funded by donations and has put an estimated budget of $20 million on the project.
"We cannot match the original in terms of the size of the entire temple complex. But we will try what we can with the land and the means that we have," said Kunal.