Tea House Garden: a garden within the garden. SJG has one with the Shoseian Teahouse inside; check with the entrance gate or official Park web site for dates of tea presentations and admission. Enjoy The East-West Chanoyu Center (EWCC) website, which includes explanation of Chado tradition.
Here is a good resource on Japanese Tea Ceremony, including different traditions of Tea Schools, history and theory.
Plus a link to Wikipedia article on Japanese Tea Ceremony
And, a youtube link to Tea at Koken; once there, you will find other video-clip offerings of tea presentations.