The usual way is to jackhammer a big hole or several in the bottom of it for drainage, partly fuill it with dirt, then break down the walls to a couple of feet below soil level - dump the busted stuff in the bottom of the pool - and start hauling dirt with a Bobcat or a small frontloader.

It's not easy.

The other option is to build a deck over the pool. There are a few companies in Phoenix that specialize in that.

If you cover it with a deck, make sure you have a way to drain rainwater out of it or you have mosquitoes breeding in the basement.

WHY fill it in ... turn it into a GREENHOUSE ...

this Mesa family did just that, complete with aquaponics ...

Here is a link that might be useful: Garden Pool

coolest thing ever!!!!

Garden pool family are my heroes! I'd love to do that to my pool....