Gunma: Kusatsu Onsen's Hot Water Field and the Tomioka Silk Mill

Kusatsu is consistently ranked among Japan's best onsen towns, built around a steaming central yubatake ('hot water field') where mineral-rich water cascades down wooden channels. Because the water is naturally very hot and acidic, staff traditionally perform yumomi — stirring the water with long wooden paddles to cool it — sometimes as a scheduled public demonstration. The sulfur smell is strong and takes some getting used to, but the baths themselves are worth it.

Tomioka Silk Mill is a UNESCO World Heritage site — a Meiji-era factory that helped modernize Japan's silk industry using imported French machinery and techniques. It's less visually dramatic than a castle or shrine and appeals more if you're interested in industrial history than in a typical scenic stop.

Gunma gets relatively few foreign visitors and isn't well set up for spontaneous same-day trips without a car — bus and train connections to Kusatsu from Tokyo exist but take a few hours, so it works best as an overnight rather than a rushed day trip.