On Friday, Mayor Ed Lee announced that Salesforce -- a global enterprise software company -- signed a lease with the city worth nearly $340,000 for 400,000-square-feet of office space on 50 Fremont Street in downtown San Francisco. The agreement marks the biggest long-term lease in the city in a decade.

"Salesforce.com’s decision to continue their expansion in San Francisco is positive proof that our city and its workforce are perfect for growing technology and innovation companies," said Mayor Lee in a statement. "I look forward to watching Salesforce.com's continued success as we work together to continue to create jobs right here in San Francisco."

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The new building at 50 Fremont St. is estimated to create space for about 2,000 employees, infusing much-needed jobs into San Francisco. Mayor Lee, who has pushed to expand San Francisco's business presence with his Start Here, Grow Here, Stay Here campaign, expressed palpable excitement over the lease.

Friday's announcement came as the latest development in Salesforce's massive expansion plan that now includes campuses in San Mateo, downtown San Francisco and Mission Bay. (Surely soon to be known as the business plan that ate San Francisco.)

Though the acquisition of 50 Fremont St. will be a major move for Salesforce, the most impressive details of the company's expansion plan are at the Mission Bay campus -- Salesforce's Global Headquarters. The 14-acre property (right near the ballpark) is set to include four separate buildings with two million square-feet of offices, retail spaces, plazas, restaurants, childcare, parking and an enormous outdoor television screen to broadcast public programming.

Unlike other business campuses, the Salesforce headquarters will be open to the neighborhood, allowing residents to access the businesses, public space and childcare, supplying a major source of revenue for the area.

Though the designs are not finalized, architecture firm Legorreta and Legorreta has released the initial plans for the Mission Bay campus. Check them out in our slideshow below:

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