Pebble Tower

I hopped down the porch steps onto the garden walkway, where a scattered cluster of smooth river pebbles caught my eye. Time for a structural balance test! I hauled a wide, flat grey stone onto the center of a flagstone paver to lay a solid foundation. Next, I hoisted a rounded brown pebble and nudged it flush over the center of mass. The real challenge was stone number three—a tiny, egg-shaped black pebble. Bracing my boots against the stone seam, I lifted it overhead with both hands and eased it onto the apex millimeter by millimeter. Zero wobble. Three stones locked in perfect gravitational alignment!