Entrepreneurship's Greatest Challenge: Rebuild Detroit
Dominating downtown and an imposing symbol of the auto industry's grip, the Ren Cen was financed by Ford but has been GM's headquarters since 1996.
Square Feet: 5.5 million
Office Occupancy: 95 percent
Long Road: Despite the auto bailout's success, Michigan has regained only a fraction of the 800,000 jobs it shed from 2000 to 2010.