Rise early and look down on a sea of clouds
On clear, windless mornings, cold air settles in a mountain basin and fills it with a white sea of clouds. Arrive at a lookout before dawn, wait, and watch mountains and even a castle rise out of the white. It does not form every day, so check the forecast the night before; most of these lookouts need a car or a taxi from the station.
A terrace near the top of a mountain at a resort in central Hokkaido, reached by a gondola ride of about 13 minutes. On good mornings the clouds spread below you like a white sea, and you can watch with a hot drink from the cafe. It opens only from about mid-May to mid-October, and the gondola must be booked in advance.
From a lookout on the mountain opposite, you look down on Bitchu Matsuyama Castle, a hilltop castle whose original wooden keep still stands and seems to float on the clouds. The clouds form most often at dawn from autumn to spring and are thickest in late autumn. The path is dark before sunrise, so bring a flashlight; the town of Takahashi is under an hour by train from Okayama, and the last stretch needs a car or taxi.
A hilltop lookout above Takachiho, a mountain town in Miyazaki, Kyushu, known for its gorge and its old myths. On autumn mornings the basin below fills with cloud, and the mountains of Aso line up beyond it. The lookout is a few steps from the parking lot, so you can wait in the car until dawn, but you need a car or taxi to get there.
A lookout on the rim of Aso's huge caldera, the ring of mountains left by ancient eruptions in Kumamoto, Kyushu. On cloudy-sea mornings the towns on the caldera floor vanish under white, and the five peaks of Aso rise above it; people say their outline looks like the Buddha lying down. You need a car, and the roads on the rim can freeze in winter.