Snake Indian Falls is always my answer.

The falls are actually located in Jasper National Park, up the Icefields Parkway from Banff. The falls are not a family excursion, nor a day trip by any stretch of the imagination. It's a 5 hour drive from Banff to Jasper (taking your time), and then another hour drive along the Celestine Lakes Fire Road (a nightmare in-and-of itself) before you reach the trailhead. Then it's a long 12 and a half miles on foot or on a bike along a boring gravel roadway to the falls.

The difficulty in reaching the falls accounts for its solitude- certainly not the vista of the falls themselves.

Snake Indian is arguably the most spectacular falls in Canada.

So why don't people go there?

Please see the above remarks...

If you'd like to visit the falls, start from the Jasper townsite. Head east on the Icefields Parkway (towards Banff) and take the exit for the Snaring Campground. This is where the Celestine Lakes Fire Road begins.

Carefully read the informational sign, as the Fire Road is single lane and time restricted (i.e. you may start driving Eastbound from 1pm to 2pm ONLY, or westbound from 3pm-4pm ONLY, etc.)

At the end of the Celestine Lakes Fire Road is the trailhead for the remote North Boundary Trail. 22 kilometers (or about 13 miles) down this trail is Snake Indian Falls.

Be careful at the lip of the falls as they are very powerful. Also watch for grizzlies, as this is their prime habitat.

You can bike to the falls and back in a long day, or make it an overnight backpack.

There is a backcountry campground near the falls complete with bear cables, but you must have a free permit from the Jasper National Park service to camp here. (780) 852-6176

Before embarking on this trail, I highly suggest you acquire a copy of the Canadian Rockies Trail Guide, which exhaustively details getting to the trailhead and the hike itself.