Zhengfu

The City of Gold was a massive Yobanjin fortress that bore the mark of Isawa on its gates.

Isawa's Last Wish
Mirumoto Temoru spent time within the city and learned the Yobanjin language. From his studies Temoru concluded that Isawa had been born in that area and that an ancient race had created something very similar to the Isawa's Last Wish long before Isawa lived.