There are many unique ancient megastructures in Japan, which can’t be found in any other part of the world. They are called “kofun”, which means ‘ancient mound tomb’ or ‘ancient grave’ in Japanese. The best known is the Daisen Kofun, measuring 480 by 300 meters (1574 by 984 feet) and with a height of 35 meters (114 feet), but there are many others as well.
From the ground, kofun structures often look like just another hill, mound or mountain. But when you look at them from the air, you can clearly see their unique keyhole shape. A keyhole-shaped kofun is typically a tumulus divided in a part where a person of royal descendance was buried (the round part of the ‘keyhole’) and a space for the performance of rituals.
Kofuns are thought to have been built between the third and seventh century AD. The stories of their construction are similar to those of the Egyptian pyramids and other ancient megastructures: it took thousands of workers and several years to build them.
This geometric structure that NASA’s Curiosity rover located on Mars is very similar to the ancient structures that still remain in Japan to this day. We can’t be sure if there is a link and it could very well be that this similarity is just a coincidence but it is interesting nevertheless.