Queenstown can often be a bit too busy for me (in comparison to Wanaka and other favorites), but it's understandable why it has so much foot traffic since it's the epicenter for adventure activities on the South Island of New Zealand. To find a bit of quiet, I head down on the lake. These mountains you see in the photo are called the Remarkables and I don't think there's a more perfectly named mountain range in the world.
After your big day of hiking, biking, frisbee golfing, jet boating, bungee jumping or sky diving- I'd encourage you to head down to the waterfront during that golden hour before sunset. Walk out along the boardwalk and watch the colors change on those mountains and be swept away. If it's a warm night, jump on in the water with the locals for a bit of a swim.