Marukoma Onsen Ryokan

Marukoma opened in 1917. Its founder Sasaki Hatsutaro had found the spring on the shore of Lake Shikotsu two years earlier. The famous bath is the noyu (natural pool) at the water's edge. Only a line of rocks separates it from the lake. Hot water seeps up through the gravel underfoot, and the depth shifts with the lake level through the year.

The spring comes out clear and colourless at 54°C, and every bath in the house looks out on the lake. The inn is off the grid. It makes its own electricity and draws its water from Shikotsu, and the Finnish sauna lets you pour your own löyly before a cold plunge in lake water. Two private baths can be booked, and one of them has a barrel sauna.

Dinner is kaiseki, and one course is cooked over an irori (charcoal hearth). Breakfast is a buffet. New Chitose is about an hour away by car, so this makes a strong first or last night. Rusutsu is roughly an hour west when you want a riding day.