The city of Calgary has not much to show but when you go there is worth staying at the HI Calgary City Center.
I stayed there for all most one week to get some rest from previous traveling and preparing for the Rockies. The facilities are well maintained and clean as I like it. Some times the C-Tram crossing gate is bit anoying when you try to fall asleep but close the window and there is nothing between you and your sleep. The included breakfast (Panecackes, toast, jam, cofe etc.) is a good reasons to get up.
The receptionists were allways friendly and helpful (Thank you Jason for helping me with the car rental.).
So if your going to visit Calgary for whatever reason consider spending the nights in the City Center hostel.