One of my favorite spring hikes is in Banff National Park, along the shore of Lake Minnewanka, the largest lake in the park. The trail is relatively flat, with only a few hundred feet of vertical gain. And you can walk a long way with unobstructed views of the lovely Rocky Mountains, especially of Mt. Girouard across the lake.
During the late summer the trail is closed to hikers, except to tight groups of four or more, because this is prime grizzly bear grazing habitat. Mom grizzlies and their cubs frequent the open bush around the trail -- and you definitely don't want to get between a sow grizzly and her cub. The trail reopens after the Labor Day weekend in September.