 It is often nicknamed "The Big O" as a reference to both its name and to the doughnut-shape of the permanent component of the stadium's roof, though "The Big Owe" has been used to reference the astronomical cost of the stadium and the 1976 Olympics as a whole.It has never had an effective retractable roof, and the tower (called the Montreal Tower) was completed only after the Olympic Games were over.In December 2006 the stadium's costs were finally paid in full.