Pyramid Lake with Pyramid Island in the middle is an iconic spot easily reachable from downtown Jasper. You can rent a bike in town and then ride to the lake. Jasper has excellent bike trail systems connecting trails around town and nearby lakes.
There’s a viewpoint with the famous red chairs, located at the most stunning photo locations in the Canadian Rockies. You might even get some company as local bighorn sheep and mountain goats like to hang out at the viewpoint as well.