Devon World Headquarters At 850 feet, the new 50-story world headquarters building for Devon Energy is the tallest building in Oklahoma. Thornton Tomasetti provided structural engineering for the project, which houses a seven-level rotunda, a six-level podium, below-grade parking, and a 300 seat auditorium, in addition to the tower. In total, the project encompasses approximately 1.8 million square feet. The scope of services also included a vertical expansion and addition to an existing precast concrete garage that connects to the new tower.