At one time, each desk in every Calgary downtown office tower was filled. Now, walking the halls in many buildings is eerie. And Calgary Economic Developmentsays it could take 15 years to fill the empty floors.

In the penthouse suite of one office tower Global News recently visited, the last tenant left the furniture behind. “No one is denying it anymore,” Greg Kwong of CBRE Limited said. Kwong has been in the Calgary commercial real estate business for decades. His global firm predicts the vacancy rate…