I went to Koya-san at the end of my month-long stay in Japan. Stayed at the Sekisho-in, at the east end of the town. After morning service (Shingon) and breakfast, walked to Kukai's mausoleum. The cemetery was serene, with the snow filtering down between the aged cedars. It was like an open-air cathedral, and the walk akin to a pilgrimage (which is probably how the Japanese experience it). My map indicated that many of Japan's military leaders have their tombs in the cemetery, and "burial" there is akin to that of Pere Lachaise in Paris.
Later saw the Dai-to or great stupa/pagoda. Aside from its' proportions, I was more impressed by the three-dimensional manadala that was created inside. Apart from the artistic quality of the sculpture (which is modern), for me it conjured up the image of the 'axis mundi', that Borobadur in Indonesia does. Circumabulated the altar five times before departing. I'd go there again, though for many, it might remain a curiosity for them.
In the motuary temple (just short of the actual mausoleum) a monk was conducting a fire ritual at one of the chapels.