In the morning we drive to the parking lot outside the park to catch a bus (reservations required) into Lake O'Hara Lodge. When we arrive at the lodge, we head off to Lake McArthur as our luggage would be automatically transferred to our cabin, but would be a couple of hours later. It was about 4-5 hours, 1300 feet elevation gain, round trip, depending on which trails you use and how many photos you stop to take! But well worth it!