Rock Ship of Masuda

A megalith shrouded in mystery, this large stone measures approximately 11 meters from east to west, 8 meters from north to south, and 4.7 meters in height.
It is said to weigh as much as 800 tons, and there is a hole in the top that is 1.6 meters wide and 1.2 meters deep. Who made it and for what reason is a complete mystery.