As construction on the 300,000-square-foot “Catalog” addition at the base of Willis Tower progresses, crews recently completed the large curving skylight capping the project’s upcoming retail and dining hall. The swooping 240-pane diagrid window will not only flood the space with light, but provide unobstructed views of the famous 1,453-foot-tall skyscraper above.

Designed by the Chicago office of global architecture firm Gensler, the overhaul of the building’s base is the most visible part of a larger $500 million renovation plan unveiled in 2017. Its Catalog name—a nod to the tower’s former namesake tenant, the Sears Roebuck Company—was revealed along with updated renderings last fall.

As the Catalog’s new skylight comes together, the project continues to sign retail and dining tenants. The most recent addition to the lineup is Brown Bag Seafood, as first reported by Eater Chicago in April.

It joins other confirmed tenants such as Urbanspace, Convene, Shake Shack, Sweetgreen, Starbucks, and Market Creations. Catalog is expected to be complete in 2020, but its first retailers will open sometime this year, according to EQ Office.

In addition to Catalog, the Willis Tower renovation includes more than 125,000 square feet of tenant amenities, a 30,000-square-foot landscaped roof deck, a modernized elevator system, and updated lighting for the building’s iconic twin antennas.

For a quick recap of the skylight’s construction, check out this time-lapse video.