Marimo (毬藻) moss balls are actually a type of algae that grows spherically as it rolls in the water. Because they only grow 5mm a month, they are easy to take care of, but they are also very rare and can only be found in a few parts of the world including Japan & Iceland. Because of their rarity and beauty, a festival called Marimo Matsuri takes place every year in Hokkaido, Japan where all the marimo plants in the Lake Akanko are taken out, individually cleaned, and placed back into the water. Not only are they adorable, but they are considered a national treasure in Japan!