You stay, when you stay here, in a temple, one of the 53 (out of 117 in all) that offer shukubo, or temple lodgings. You get up at dawn (if you are sensible) to witness the morning chants and goma fire ceremonies in which the monks, by burning 108 pieces of wood (108 is a sacred number in Buddhism) and then scattering 108 white sesame seeds on top of them, believe they are purging their illusions and replacing them with spots of enlightenment, bringing the Buddha into their bodies. By seven-thirty every evening, the main street in the mountain village is largely silent and all its shops are shuttered. Even in early afternoon, when I arrived, very few figures were visible—only a nun in blue robes and then an abbot in a black gown, clacking away on traditional geta wooden sandals while a shaven-headed young acolyte hurried to keep up with him.

I walked down the little street (the whole town has a population of four thousand—plus a thousand monks—though once there were more than fifteen hundred monasteries here) and stepped through the gates that led into the fourteenth-century temple where I was to stay the night. A head monk called a hello and then, seeing how I took off my shoes in a non-prescribed, non-Japanese fashion, shouted at me, "That's wrong!" Then he led me up to an exquisite four-room, blond-wood tatami suite, complete with a sleek TV, remote-controlled heating, a heated toilet seat, a private shower and bath, and even a cup in which to make café mocha. Drawing back the shoji screens, I could see a classic Japanese garden with a stone lantern and stone bridge.

Dinner would be served at five-thirty, he said—it would turn out to consist of twelve lacquer bowls of delectable food cooked in the traditional Japanese Buddhist way, without meat or fish or garlic or onions: the local specialty, sesame tofu; mountain vegetables; and sweet-and-sour seaweed in vinegar sauce. A morning service would be held the next day at dawn. Then there would be a traditional Japanese breakfast.

I went out for a walk after dinner along the chill, silent streets, and when I got to Ichi-no-hashi Bridge, all I could see was a long trail of stone lanterns, each one giving off a faint light, leading through the graves and the tall cedars to where Kobo Daishi is believed to have been sitting in eternal meditation for 1,172 years. I felt as if I had stepped into a whole pulsing, thrumming mandala, or Buddhist diagram of heaven—the rare place in Japan that seemed to turn with a mystical intensity.

Then I hurried back to the temple; its great wooden gates close to the world every night at eight.

In almost any Japanese home you visit, you will find in one corner a little platform that functions as a household shrine of sorts. On it will be a few ceremonial objects, a picture or two of departed loved ones perhaps, maybe a Buddha. Koyasan is like the secret shrine hidden in one corner of the old household that is known as Japan, a repository of the ancestral and the deep, without which, some believe, the modern, bustling country would not be able to function. It sits near the very center of the nation, tucked within a ring of eight outer and eight inner mountains that cradle the town like a hidden treasure within a set of lotus petals. From here you can't see anything of modern Japan below, and the businessmen in their suits, the perky girls in their cowboy hats and miniskirts, can't see you.