Peak Season: Summer
There are more than a dozen campgrounds in Banff National Park. Many campgrounds fill up, especially at Lake Louise.
Banff is the only park in the Canadian Rockies that I heard before I headed across the border. It's notable for good reason, but if you are speaking in terms of pure natural beauty I think I would head elsewhere.
Banff is well known, and due to this notoriety it's very busy. The town of Banff is a bustling commercial center whose entire economy is dependent of tourism. Then there's Johnston's Canyon just to the North of Banff. This is the most trafficked hike in the park and I really don't see why. It's a nice trail, and he waterfalls are alright, but there are many sites that are far more breath-taking elsewhere in the park.
Then there's the Columbia Icefield. It's a big old chunk of ice, but that's about it. It's not nestled in a particularly beautiful part of the Rockies. It's really just a dirty pile of ice and snow.
Another heavily trafficked area is the Lake Louise area. If you see a postcard perfect picture of Banff it's probably the mirror reflection of the mountains off of Lake Louise. This area is a hiker's paradise and you only need to hike a few miles to find some solitude from the throngs of people that sit lake side or paddle about. Banff is nice, but Yoho and Jasper are nicer.