The unfathomable scale of the world's largest religious festival in India overshadows many nations in size -- and for the economy, its impact is just as dramatic.

"Business is booming everywhere for everyone across our city," said taxi driver Manoj Kumar, whose northern Indian home of Prayagraj has swelled from its normal seven million residents dozens of times over.

Religion, politics and the economy are deeply intertwined in India -- and the six-week-long Hindu festival of the Kumbh Mela gives one of the clearest examples.

The Hindu nationalist government of Prime Minister Narendra Modi has poured in funds for large-scale infrastructure upgrades.

"We are seeing an unimaginable transformation of our city," 37-year-old Kumar said.

"There are new roads, bridges, additional flights and trains, new hotels and restaurants, and an unmet demand for workers."

The Kumbh's extraordinary scale provides a major job boost, with millions of visitors splashing out on accommodation, transport and food.

Kumar's daily earnings shot up to around $250, roughly eight times as much as usual.

"I've had some of the busiest 18-20 hour workdays of........

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