The mating nest of a Japanese pufferfish. The fish is 5 inches long and spends 30+ nonstop hours creating this 6 foot mandala on the ocean floor to attract Mrs. Pufferfish. Then they snuggle and things happen. She then leaves while he flattens an area in the center and builds up a hill of sand, where she returns and lays her eggs.
A 5 inch long FISH makes this, with no brain, no self awareness, no hands, no nothing. It blows my mind, even more than the perfect spirals of the sea shells snails make. Nature is amazing.
Check this out--it's short.