Yes, I imagine that the beds shown below would be good gold fish ponds in some places.
I don't go for "below grade" because I don't feel that is necessary here. The paths are below grade about 4" and, like Dilbert, that soil is added to the growing space. It has just worked out that nearly all beds in my gardens are about 25' long and 4' wide.
Often, I will run the tiller when I'm starting out building a bed. The weeds in the paths may well see that tiller going up and down thru them during the season.
Just as I have gotten everything in beds again last year, there will be new ground in an expansion of the "big veggie garden," this year. I will start off with row crops, maybe for a few years. Meanwhile, I will try to
figger how to get that ground in beds, too.
Steve
Picture from the Library of Congress, 1927 Zuni gardens in New Mexico (and, here is a link to more Zuni gardens, past & present
[click]):
We are each other's harvest; we are each other's business; we are each other's magnitude and bond. ~ Gwendolyn Brooks