The overlook of the Lusail Stadium for the World Cup 2022. Photo: Courtesy of CRCC

The China Railway Construction Corp (CRCC), one of the country's two biggest rail construction contractors by revenue, on Monday completed laying the lower-level cable chain of a canopy-supporting structure for the Lusail Stadium, the 2022 World Cup's main stadium.

The development means construction has entered the most challenging phase, the company said, as the fish-belly-shaped cable net is the world's largest by span. Lusail Stadium is designed to be the world's largest membrane-structure building, incorporating 45,000 square meters of membrane.

The laying project, which connected a total of 16 96-meter-long, 9-centimeter-thick steel cables, took nine days to complete. Each single cable weighs 6 tons.

The round chain forms an inner circle with a diameter of 122 meters, which is the "eye" of the stadium's bike-wheel-shaped canopy structure.

The CRCC is the first Chinese contractor enlisted to build a World Cup main stadium.

The stadium in Doha will be the main venue to host the opening ceremony, games, finals and closing ceremony, according to Qatar's 2022 FIFA World Cup organizing committee.

The 92,000-seat Lusail Stadium has 1,000 more seats than Beijing's National Stadium, known as the Bird's Nest.

The projects required enough steel to build three Eiffel Towers.