In 1875 Calgary was born at Fort Calgary. The site today is occupied by a replica of a military barracks that stood here in the 1880s (the original fort has long since disappeared). The barracks acts as a museum of Calgary history from 1875 to the 1920s, with more than a passing nod to the Northwest Mounted Police.
Granted, it's not particularly old, but this is fast-moving Calgary, where last week is considered ancient history.