The Hudson's Bay Company coat of arms is seen on their 'The Bay' store in Toronto, Canada.

Hudson's Bay said on Monday that it will sell its flagship downtown Toronto store and neighboring office tower for $587.09 million to commercial real estate heavyweight Cadillac Fairview and open a full-line Saks store in the leased-back space.

The historic Canadian retailer has long floated plans to unlock the value of its real estate but had previously given no time frame. Its shares ended 1.2 percent higher in Toronto after spending most of the session in negative territory.