Concave rock - What to do?

[3000kelvin]

I have a piece of LR that has, what I think is, a cool concave section. I’d like to do something interesting with the section circled in the photo. Originally I was thinking of filling it with GSP, but maintaining it to be isolated to the concave section may be more work that I want to invest. Any other ideas for what I could put in this section of rock? Open to any ideas.

 

[P-Dub]

Looks like a great place to nestle a nice clam...