IMO the best outdoors place on the prairies is Calgary. Mainly because it offers top-notch year-round recreation.
The Rockies are a year round recreational area, with some of the best skiing in the world during the winter, and great hiking, canoing, camping, cycling, golfing...you name it etc.. in the summer.
To the north you've got your standard lakes, to the east and southeast, the badlands, to the west past, Banff and Lake Louise, you've got Fairmont, Invermere etc... These places aren't on the prairies but they're only 2 1/2 hours from Calgary. The Shuswap lake system, which is imo, the nicest lake system in Canada is 5-6 hours west of Calgary.
Bragg Creek and Kananaskis country are half hour to an hour away depending on where you're going.
Two of the places I've mentioned (Rocky Mountains, and the Badlands) are places that people from around the world come to visit.
Here are some pictures of Bragg Creek. The reason I've posted these is because Bragg Creek is half an hour from Calgary. 15 minutes if you live on the west side of the city.
Elbow Falls is about a half hour from the city limits.