In August, the two-block-long Salesforce Transit Center and its 5.4-acre rooftop public park opened after a decade of design and construction. The 1.2-million-sq-ft transportation hub is the core of a transit-oriented development district, rezoned for office and residential towers. In the future, the nearly $2.3-billion transit center, designed by Pelli Clarke Pelli Architects and built by the Webcor/Obayashi Joint Venture, will link to more than 10 transit systems and high-speed rail.