When Narendra Modi, then the chief minister of Gujarat, unveiled a grandiose plan to build a large statue of Sardar Vallabhbhai Patel — India’s lauh purush (Iron Man) — ahead of the civic elections in Ahmedabad in 2010, it was considered a pre-election sop. However, nearly eight years later, the statue stands tall with a towering height of 182-metre (597-feet).

Rising amid the foothills of the Satpura and Vindhyachal ranges, the statue is a dominating feature in the picturesque environs of the holy Narmada river. Only when one stands below the statue, the enormity of the structure strikes. To gauge the structure’s enormity, consider these statistics: it is over three times the height of Christ the Redeemer in Rio Dio Janerio, twice the size of Statue of Liberty in New York and nearly 77 feet taller than China’s Spring Temple Buddha statue. When Modi unveils the statue later today, on the 143rd birth anniversary of Patel, it will become the world’s tallest.

Built at a cost of over Rs 3,050 crore by an army of over 3,000 workers, including 300 engineers from Larsen & Toubro, in little over 40 months (work started in May 2015), the statue is a sheer marvel of engineering. In comparison, it took China, known for building infrastructure at lightning speed, over 11 years to build the Spring Temple Buddha statue, which is the highest in the world, for now.

The statue has been designed by a team lead by 93-year-old sculptor Ram V Sutar. Designers of the statue faced two major challenges. One, the Statue of Unity was to be designed based on a real-life photograph of Sardar Patel in dhoti and jacket, unlike the statues of Buddha and Christ, which are imagined depictions covered in robes. In short, the designers of the Statue of Unity had to capture more details than the makers of other comparable structures. Two, in a survey, 15 major Indian bronze foundries were found incapable of executing a project of this size.

To make sure the statue’s face resembles Patel’s facial features, around 2,000 photographs of the leader from archives were studied. To get his posture right, the group working on the statue chose a picture of Patel taken in 1949, arguably one of the most strenuous years of his life.

Using these pictures, Sutar built an 18 feet bronze statue of Patel. Once built, the statue was taken to his birthplace in the town of Karamsad in Gujarat's Anand district to observe the reaction of the people, including those who had seen him alive. Using the feedback, Sutar built another statue, this time 30 feet tall. After the design was finalised, a full-size digital model of the statue was prepared. Sutar then went to China along with the officials of Sardar Sarovar Narmada Nigam Limited, a Gujarat government owned firm which operates the Sardar Sarovar Dam, to get intricate bronze cladding, which could not be made in India.

World's largest foundry — the China-based Jiangxi Toqine Metal Crafts Corporation, was tasked with building these cladding, required to give the statue final shape. The sculptor had to visit China four times before the company could move ahead with the production of around 7,000 bronze plates of various sizes, which were welded together at the site of the statue. Techniques such as 3D scanning and computer numerical control production were used for accurate reproduction of minute details. After solving the jigsaw puzzle with oxyacetylene flame (that is, matching and welding), the number of cladding came down to 550. These were affixed onto the structure to give it the final shape.

Part of the statue enclosed inside the 8mm bronze cladding is a two-layered structure. The innermost layer has two 127-metre-high towers made of reinforced cement concrete. These towers rise up to the chest area. The steel frame between the towers and the cladding forms the second layer.