Banff Upper Hot Springs is the highest operating hot spring pool in Canada.
Even though it's just one pool and it usually gets quite busy, it's still a super nice thing to do after a long hike or day out skiing in Banff, especially with its location just 4 km outside of the downtown and a quite affordable price.
Note that entry to Banff Upper Hot Springs is first come, first served. The parking lot is same as for the gondola and it gets full during the summer, so you might have to take a bus form downtown.