Construction is on track at the San Francisco Museum of Modern Art (SFMOMA), where workers put the last steel beam in place on the massive expansion Wednesday, writes ABC‘s local San Francisco affiliate. The building, designed by architecture firm Snøhetta, is being erected behind the institution’s current home, the work of Mario Botta.

SFMOMA has been closed for construction since June of 2013. The old building had seen roughly 11.5 million visitors cross its threshold since opening in SOMA (short for South of Market) in 1995, and was ill-equipped to accommodate the museum’s growing popularity and collection. The museum’s holdings, which have grown from 12,000 to 32,000 artworks, were recently augmented by the 1,100-piece collection of Doris and Donald Fisher, founders of the San Francisco-based clothing chain Gap Inc.

“It’s very exciting after years of work in preparation to finally see the building coming up,” SFMOMA director Neal Benezra said to ABC. When completed, architect Chris Dykers told ABC, the new building will offer “a very calm experience. The rooms are designed to allow the art to move forward in your consciousness, so it has less sculptural identity on the interior.”

The expansion project is expected to cost $305 million. In June, the museum announced that it had already raised $570 million toward a $610 million fundraising goal that would cover construction costs and add $245 million to the institution’s endowment (see “SFMOMA Nearing $610 Million Fundraising Goal“).

A 2016 reopening is planned, adding 235,000 square feet that will include a new photography center on the third floor, where it will present the museum’s 17,000-piece photography collection (see “SFMOMA to Open the Country’s Largest Photography Exhibition Space“).

“This is going to be one of the finest museums of modern contemporary art in not just the United States, but in the world,” Benezra promises.