Noboribetsu: Hell Valley and Hokkaido's Strongest Hot Springs

Most onsen towns have one type of water. Noboribetsu has nine — sulphur, iron, sodium chloride, alum, acidic iron sulphate and others — and that variety is the reason it is regarded as one of Japan's most significant hot spring resorts rather than simply a pleasant one.

In practice this means the larger ryokan run multiple baths with different water, and you move between them. A single hotel here can offer sulphur springs for skin, iron springs said to help circulation, and a plain sodium bath, in the same visit.

Many of the big hotels sell day-use bathing without an overnight stay, which is the way to do it if you are on a day trip from Sapporo. Check times: day-use windows are usually mid-morning to late afternoon and close before the evening guests arrive.

Jigokudani — Hell Valley — is the crater immediately above the town, a bowl of grey and ochre rock with steam venting from dozens of points and a stream running hot through the middle. It is the source of the water.

A boardwalk loops around and through it, and beyond that a marked path continues to Oyunuma, a sulphurous lake, and a natural footbath in a stream where the hot water has cooled to a bearable temperature. The footbath is free, it is in the forest, and it is the best part.

The full walk is about an hour round trip and is easy. Wear something you do not mind smelling of sulphur afterwards; the smell is strong and it does linger on fabric.

This one catches people out and it is not reversible in a hurry. Sulphur springs tarnish silver, turning rings, chains and earrings black through a reaction that is chemistry rather than dirt.

Take silver jewellery off before you bathe and leave it in the locker. The same goes for anything silver-plated. Gold and platinum are fine.

While on onsen basics: you wash thoroughly at the seated showers before entering the bath, you do not put your towel in the water, and tattoos remain an issue at some establishments — Noboribetsu's larger hotels are increasingly relaxed and several are explicitly tattoo-friendly, but if you have visible tattoos it is worth confirming before you book rather than at the door.

Noboribetsu is about ninety minutes from Sapporo and sits close to Lake Toya, which is why almost every day tour pairs them.

Lake Toya is a caldera lake with a symmetrical island in the middle and Showa Shinzan beside it — a lava dome that pushed up out of a wheat field in 1943 and 1944, growing several hundred metres while a local postmaster documented it daily. That record is why the volcano is famous among geologists.

The pairing works because the two are different registers of the same volcanic system: one you bathe in, one you look at. A day trip covering both, with a bath at Noboribetsu in the afternoon, is one of the better full days available from Sapporo.

Staying the night is better still. Noboribetsu after the coaches leave, with a bath before bed and another before breakfast, is the actual point of an onsen town.