I would like to build a grotto using dry stack stones. It would be about 5 ft tall in the form of a semi-ball ie like a ball cut in half. The opening would probably be taller than wide to help support the stone.

It should have dripping water, and a shallow pond in the bottom.

Has anyone built such a thing? Have you ever seen one?

Any suggestions or advice?

The back would need to be built like a series of arches, each one smaller than the one in front of it, so the weight of the stone is on each arch, not leaning towards the front. But I have never built one - so this is a guess.

We did build an arch in a wall in a dry stack course I took.