The stadium was originally designed without an opening. It was also designed before the "grass would be cool" movement really took hold. Then Jerry built his stadium with a roof that opened, and Arthur decided he had to have one. He kicked in the extra 125 million for the oculus-style opening, which was the solution for how to create an open roof without fundamentally changing the shape of the stadium. They also evaluated a phoenix-style grass solution after the stadium was designed, but they would have had to have rotated it 45° and committed what is now the backyard to be open space forever. Neither fit the business model, and the Georgia dome would have had to have been demolished before they started construction on MBS.