Nishiyama Onsen Keiunkan hotel somehow proved they were older. (Founded in 705, run by the same family for 52 generations.)

Tofugu has a nice article about the centuries old establishments in Japan: http://www.tofugu.com/2014/10/28/over-a-thousand-years-of-se...

Yep. They discovered another one in Japan that was founded circa 700 AD.