The Athabasca Glacier is the most accessible glacier in the Canadian Rockies. It's about 100 kilometers south of Jasper, in the area of the Columbia Icefield. It is not anywhere close to the most impressive or biggest glacier you can see in the Canadian Rockies, but as it is next to the motorway, it's one of the most comfortable to visit. There is a tiny walkway that lets you access to the base of the glacier, and a specialized vehicle takes you to the central area which is interesting.
Access to the ice is restricted to the use of special shoes and should be done with expert guides since it is a treacherous area and there are many tricky areas.