Not only is the megalith huge, but as Graham says, the stonework “is so beautifully done that the gigantic stone, surrounded by a water-filled pool, appears to float lightly in the air.”
The Ishi-no-Hōden megalith is thought to have been cut from its surrounding rock some 1,500 years ago and, if freestanding, would weigh in the region of 500 tons. It sits at the centre of a pond and appears to float above the surface of the water. As with many sacred objects in Japan (including natural objects such as trees) the Ishi-no-Hōden megalith is adorned with a sacred rice-straw rope known as a shimenawa.
And here’s some video of the site found on YouTube: