Probably, you would wonder why moss has been thought beautiful. It has been regarded as one of the salient plants to let us feel SABI, the aesthetic term to describe something many Japanese are attracted to. Moss looks beautiful to us because it gives us a chance to see what has been engendered for a much longer period than a life of a human being is. In another expression, we respect and appreciate it because it is thought to be created by the passage of time or something beyond human power and capability.
Below is moss garden seen in one of the great temples in Japan, ginkaku-ji (Silver Temple).
Well, if you visit Saiho-ji, you're required to reserve a couple of months before visiting Saiho-ji. And there you're permitted to see the sights in the garden after making a handwritten copy of one passage in a Buddhistic scripture to give you calmness because it is thought concentrating into writing in a ritual or formal way would offer you a feeling of calmness and detachment.
I would recommend you to come to Saiho-ji in November because you will be able to enjoy the contrast of Moss Green with Red Leaves. When I was there, I found I had not seen such a beautiful place. I was driven to keep taking photos of the sights, but I also found my photo skill was not enough and I thought I would buy another camera better in quality enough to enable me to take better ones. Next time I go there, I will take a new camera with me.