There are a lot of articles on stacking stones. Why some people stack them… and at least as many on why you should not.

Because stone stacks are built using unaltered stones, they require your full attention on the task of the present moment to find the perfect connection of the stone’s centre of gravity to its foundation to balance the next layer. The process is meditative; it heightens present moment awareness/mindfulness. Even the simple act of choosing the stones heightens mindfulness!

I have no interest in balancing stones (the fad that seems to piss off conservationists everywhere). I just like making a little pile. I do find the process meditative.