You are probably aware of this dolmen in Nara, Japan. Sennari has just posted the link on another thread.
The interesting bit is this that this one actually has an underground passage. For what purpose?
According to Sennari,
" The stone stage（Ishibutai） in Nara Prefecture
I was told the humanity were made in the stone circles by the energy which was sent from the sky and the direction given to the stone circles around the time Stone gods descended to the earth in an early time.
The first humanity was made in the small village named 'Hoshihara' in Ayabe-city in Kyoto, Japan where Hoshinomina (alter ego of Miss Taeko Shiraki) descended.
However the creature and humanity came to be made in the stone work like the stone stage（Ishibutai） because the energy of Stone gods got weaker later."