The trail to Rawson Lake, starting at Kananaskis Lakes, is popular in the summertime. It is exciting as it skirts Upper Kananaskis Lake for its beginning, passing by waterfalls and streams along the way. The elevation starts around 1.3 km and continues climbing until Rawson Lake.
Once you reach Rawson Lake, you can walk around it and pick a nice spot to sit and relax. I suggest bringing some picnic supplies and enjoying the scenery under the mountains. It's a lovely alpine lake frequented by wildlife such as marmots and pikas. Check for closures on this one, as a female grizzly bear often dens with her cubs along the slopes above the lake.
For those looking for a more extended and challenging day, consider hiking the (very) steep trail to Sarrail Ridge. It has some surreal views over the Upper and Lower Kananaskis Lakes. Be forwarned, it is one of the most popular photography locations in the park system so be prepared for crowds in the summer.