Old shaded in-ground pool practical repurposing?

Greetings. Looking for creative use ideas for an awkward spot on my property. There is an old rectangle concrete in-ground pool in a mostly wooded section of my property. Neighbor thinks it was possibly a fish hatchery at some point but the previous owner thinks it was an old swimming pool (based on some of the ornamentals planted near there). It is about 7 feet deep with about 2-3 feet of 20 years of decayed plant material. It doesn't retain water because there is an opening (see pic) and the drain valve is rusted open.

It's an eyesore, as you can see from the pictures. I'd love to turn it into something useful for my homestead and/or maybe something that generates a little side income. Because it's in the shade for all but 45 minutes a day, growing things isn't practical. Right now there is only about 3-4 plants that have taken root naturally in there (a nettle, jewelweed and some tulip poplar seedlings). An animal pen is a possibility, but that would require shoveling out above our heads to clean. Same for composting, I suppose. Would vermiculture work in there?

Taking any and all ideas!

Add crenellations and shoot at the French?

Sorry, reading too much Napoleonic war historical fiction recently.

Could a liner be added to retain water?

Your description sounds like this would make a great garden bed for shade loving edibles:

https://permies.com/t/40/10302/Shade-Tolerant-Edibles

https://permies.com/t/215110/Good-plants-deep-shade-food