Takaragawa Onsen Osenkaku is a secluded one-inn hot spring ryokan nestled in the mountains of Mt. Tanigawa in Minakami Town, Tone District, Gunma Prefecture. Founded in 1923 (Taisho 12), this historic inn is known for its giant outdoor bath complex with a total area of 470 tatami mats, among the largest in Japan. It became famous as a filming location for the movie 'Thermae Romae' and was selected as one of Lonely Planet's Top 10 Hot Springs in Japan, making it internationally renowned.

There are 4 outdoor baths, each with unique characteristics:

1. **Kodakara-no-yu**: The largest outdoor bath at 200 tatami mats, accommodating 200 people at once

2. **Maka-no-yu**: 120 tatami mats, a historic outdoor bath built in 1940 (Showa 15)

3. **Hannya-no-yu**: Mixed bathing outdoor bath

4. **Maya-no-yu**: Women-only outdoor bath

The hot spring is a simple hot spring (alkaline hypotonic high-temperature spring) with a source temperature of approximately 70°C and a total flow rate of approximately 1,800 liters per minute. All outdoor baths use 100% source water flow-through. The water is colorless and transparent, said to be effective for neuralgia, muscle pain, joint pain, sensitivity to cold, and fatigue recovery.

Accommodation rates start from 32,800 yen for 2 people per room (tax included). Day-use bathing is available for 1,500 yen for adults, operating hours 10:00-16:30. Check-in is at 15:00, check-out at 10:00, and the inn is open year-round.

Access is by free shuttle bus from JR Joetsu Line Minakami Station (reservation required) for about 30 minutes. By car, it's about 25 minutes from Minakami IC on the Kanetsu Expressway. Free parking is available. In winter, studless tires or chains are essential due to heavy snowfall. It's a famous hot spring where you can experience open bathing in nature at one of Japan's largest outdoor baths.