The tongue of the Athabasca Glacier runs from the Columbia Icefield to within walking distance of the road opposite the Icefield Centre. It can be visited on foot or in a Snocoach bus. It has retreated about 2km since 1844, when it reached the rock moraine on the north side side of the road. To reach its toe (bottom edge), walk from the Icefield Centre along the 1.8km Forefield Trail, then join the 1km Toe of the Athabasca Glacier Trail.
You can also park at the start of the latter trail. While it is permitted to stand on a small roped section of the ice, do not attempt to cross the warning tape – many do, but the glacier is riddled with crevasses and there have been fatalities.
To walk safely on the Columbia Icefield, you'll need to enlist the help of Athabasca Glacier Icewalks, which supplies all the gear you'll need and a guide to show you the ropes. Its basic tour is three hours; there's a six-hour option for those wanting to venture further out on the glacier. Hikers must be at least seven years of age.
The other, far easier (and more popular) way to get on the glacier is via a Snocoach ice tour offered by Brewster in conjunction with its Skywalk tour. For many people this is the defining experience of their Columbia Icefield visit. The large hybrid bus-truck grinds a track onto the ice, where it stops to allow you to go for a 25-minute wander on the glacier. Dress warmly, wear good shoes and bring a water bottle to try some freshly melted glacial water. Tickets can be bought at the Icefield Centre or online; tours depart every 15 to 30 minutes.