Pools are great fun in the summer, but an outdoor pool isn't very useful for swimming in cold winter climates. Convert it to another use during those cold weather months so it's not just a giant hole in the ground.
Allow your old pool to continue to be used for swimming, but for fish instead of people. With it being constructed to hold water, you can convert it to a koi pond or pond for other animals such as frogs and small amphibians. Add some rocks and vegetation to help convert it from a pool to nature's play area.
Use your old pool for a storage area. During the fall and winter months you can use it to keep your yard organized and keep your firewood dry. Empty your leaves from raking your yard into the pool until you have time to bag the leaves and take them to the dump. The pool can also be used for storing firewood. Place your pool cover on top of the leaves and wood to protect it from rain, snow and wind.
Your old pool can become a very large sand box. Drain the water from the pool and fill it with sand. You can create your own little beach in your backyard. With the depth of the pool, it can be used to play games such as treasure hunts; bury treasures in the depth of the sand and let the children or adults dig for treasure.