The hot spring pool is the entire site. Macaques sit in the water with snow on their heads, groom each other, and squabble at the edges, entirely indifferent to the ring of people photographing them from a metre away. Young animals play in and out of the water constantly.

The valley path to the park, a walk of around 30 minutes through cedar forest from the car park, is worth taking slowly — monkeys move along it and are often encountered on the way in.

The surrounding forest holds the troop when they are not at the pool, and on warmer days they may not come down at all — the bathing is a cold-weather behaviour.

January and February are the peak, when snow is deep and the contrast between steam, snow and red faces is at its best. The park is open year-round and the monkeys are present throughout, but without snow the photographs are ordinary.

Practicalities

The park is reached from Yudanaka or Nagano, easily done as a day trip from Tokyo by shinkansen and local bus. Staying in a nearby onsen town lets you arrive at opening time before the tour groups.

The walk in is icy in winter — proper footwear or crampons matter. Do not touch or feed the monkeys, do not make eye contact with adult males, and keep food out of sight; they are wild animals and will take what they can. Note also that this is a single, small, crowded site: it delivers exactly what the photographs promise and little else, so plan it as a half day rather than a destination.