LAS VEGAS (KLAS) — Construction work continues on MSG Sphere at The Venetian, as crews reached a milestone this week with the completion of the project’s heaviest lifts to date.

The largest man-made sphere in the world is a work in progress behind the Venetian and the Palazzo. It is designed to be the best acoustic venue ever built.

Using the DEMAG CC-8800, the fourth largest crawler crane in the world, construction crews assembled two massive 240-ton steel girders that sit 140-feet off the ground and span the length of the venue’s eventual stage, MSG Entertainment shared in a press release Wednesday.

The massive steel girders are made up of two 137-foot long, 120-ton U-shaped steel tubs to make the bottom halves, and two more 120-ton steel tubs were hoisted 140-feet in the air and secured into place to make the top halves.

The girders will each be filled with 300-cubic yards of concrete, which will help bear the weight of the venue’s 13,000-ton steel domed roof.

MSG Entertainment says vertical construction will continue through the rest of 2020, with work on the roof planned to begin in early 2021.

“Placing these giant steel girders is a critical milestone for MSG Sphere and a unique element of building a truly spherical venue. This technical work allows us to continue vertical construction, and will also help provide support for the 13,000-ton steel domed roof, which we anticipate we will begin building in early 2021,” Nick Tomasino, VP Construction for MSG Entertainment said.

When the COVID-19 pandemic hit Las Vegas, the project was temporarily suspended. Construction has since resumed and officials expect the project to be complete in 2023.