I thought I was doing good with creating a square-foot-garden with my kids (http://www.toddalewis.com/square-foot-gardening.aspx)... hard to compete with an "indoor" swimming pool.
I actually worked building pools during one summer[1], so I would have went a more traditional poured concrete route. I probably would have also had a plan to fill the pool in and cap it with concrete if I planned on selling the house.
Kudos on the indoor garden - I was just thinking of building one, but spring is near.
[1] Caveat - I worked almost every variety of job during high school in a small town...so the 'experience' factor is minimal. Mechanic several times/several farm jobs/baker/librarian/general contractor/factory/etc
There was no digging involved when putting in the pool, he just put it down on top of the old garage floor.