ExxonMobil Corporate Headquarters, Texas

ExxonMobil is the largest of the six supermajor oil companies, and, with over $400 billion in revenue in 2014, it was the largest publicly traded company of any kind in the world, exceeding Walmart in sales (though not in number of employees, despite having over 75,000). ExxonMobil's upstream operations are mostly managed by offices around Houston, and the company's large chemical division is headquartered next to BP's campus on the I-10 Energy Corridor. The headquarters, located in the northern suburbs of Dallas, off the John Carpenter Freeway, are hard to see, tucked inside a leafy campus with a fenced perimeter, and a closed gate.