The Transamerica Pyramid's peaked roof has been a defining element of the San Francisco skyline since the tower's completion in 1972. At 260 metres — or 853 feet — it's also the tallest building in the city. But it won't be for much longer. The 326-metre (1,070-foot) Salesforce Tower by Boston Properties and Hines is well under construction, and its steel-framed floors are starting to make a bold impact. 

Salesforce Tower rendering, image via Pelli Clarke Pelli

Pelli Clarke Pelli Architects won an international competition in 2007 to design the tower and the adjacent Transbay Transit Center. Together with Kendall / Heaton Associates, they've imagined an obelisk-like office tower that will offer 61 floors and 1.4 million square feet of space. The building's facade will be composed of clear glass and highlighted with pearlescent metal accents which taper in depth to emphasize the curved corners. A transparent crown and a vertical zipper element that will be illuminated at night mark the pinnacle of the tower. 

Salesforce Tower and Transbay Transit Center, image via Pelli Clarke Pelli

Metal sunshades will be affixed to every floor to maximize sunlight penetration while reducing solar heat gain. In addition, heat-exchanging coils around the building's foundations may provide cooling, while water recycling systems will help reduce unnecessary waste. Tenants will enjoy direct access to the Transbay Transit Center and its landmark rooftop park which symbolizes the development's commitment to sustainability. 

Salesforce Tower's climbing steel frame and core, image by Brianne Benness

Recent photos from the site show the tower's steel floor plates wrapping around the growing concrete core up to the eighth level. The building's curved profile is taking shape and the tapering effect will soon become a prominent feature for onlookers to gaze upon. You can track the progress of the tower by visiting the official website, which offers a look at construction via several webcams. 

Salesforce Tower's position in the streetscape, image by Brianne Benness

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