Japan's most secretive, sacred and important place. It is believed that in 4 BC it was built. Apart from the royal family and Priest of Japan, no one has been able to enter here till date. This suture is broken every 20 years and is rebuilt again. Why so much privacy ??? According to historians, many old documents of the Japanese empire are hidden there, which have never come before the world. And know, the Japanese have to protect religious privacy but they are great! 
Source:
https://m.priyo.com/articles.