Skidmore, Owings & Merrill are a huge global firm (now known as SOM) famous for very large projects: they designed the Sears Tower (now Willis Tower), which was the tallest building in the world for quite a while; they also designed One World Trade Center, currently the tallest building in America, and the Burj Khalifa, currently the tallest building on earth. In Pittsburgh, they designed 20 Stanwix Street, a 22-storey minor skyscraper along the Monongahela, which is not quite as big as the Burj Khalifa. They also designed the YWCA downtown on Smithfield Street and the PNC branch bank at Fifth Avenue and Craig Street in Oakland. Working for Skidmore, Owings & Merrill, Natalie de Blois designed the Equibank Building, now Two PNC Plaza, which at the time was the largest building in the world ever designed by a woman.