Cellars for beer, water, or food storage; oh my

So in my playing in the dirt last weekend to figure out the pipe that I ran into while digging my fence post, I also explored a couple other depressions that I noticed in my back hillside. The first depression turned out to be yet another old pipe that exits out the side of the hill. The second however just kind of kept going and growing. It started with pulling a few bricks and stones out until I realized that I was at the top of an arch. Then I began expanding the sides to unveil the whole scope of the arch and finally I dug deeper into the arch, which began to curve to be more of a dome shape.

Based on the old insurance maps of this back lot from 1904, there used to be some small 1 story structures as well as a stable located here. I think that this was probably a food storage (or who knows maybe even beer storage) cellar for the family that lived here to refrigerate their food. It was probably built below the 1 story that is shown on the map; semi into the hillside, so it was counted as a basement.

Either way it looks like its only the end of the old cellar with the rest of it being demolished when the 1 story structures were bulldozed. Now I'm kind of just brainstorming what to do with it now. Grotto? Fire hearth? Any better ideas? It looks like it's to the side of the courtyard enough that I'll be able to still make steps down on the right side of this.