salt's cation — pairs with chloride to make the water salty.
Chloride Cl⁻
table-salt anion — coats the skin and holds heat in.
Known good for
Warmingcold sensitivity
Skin conditionsatopic skin, eczema
Circulationtired legs
Sensitive-skin cautionbroken or dry skin
A sodium- and calcium-led, sulfur-bearing chloride spring. At the source the water is faintly pale yellow and clear, with a light salty tang and the characteristic rotten-egg note of hydrogen sulfide. Weakly alkaline and soft on the skin, it is moderately mineralized with noticeable body, and carries a real sulfur load (total sulfur 12.1 mg/kg).
Sampled at wellhead·Analyzed Oct 10, 2024·日本水処理工業株式会社
Hotel Urashima is a large resort spread across several buildings along the Nanki-Katsuura (南紀勝浦) coast, with onsen baths built into the hillside and shoreline. The two most talked about are Bohkido (忘帰洞) and Genbudo (玄武洞), both set inside natural sea caves where the bathwater opens straight onto the ocean. There is also Takinoyu (滝の湯), named for the sound of a nearby waterfall rather than being a waterfall-shower bath itself, and Yoho no Yu (陽宝の湯), a panoramic bath high up in the mountain building. Moving between buildings means riding a long escalator built into the hillside, and guests arriving from the harbor come in on a turtle-shaped shuttle boat, a nod to the Urashima Taro (浦島太郎) legend the hotel takes its name from. It sits in an onsen town long tied to pilgrims walking the Kumano Kodo (熊野古道), and rooms here come with their own private onsen bath alongside the shared ones.
653. Hotel Urashima, Nachikatsuura, Wakayama (pt.1) ★★★
A great onsen carved into rock. The hotel has 7 bathing zones available for visitors accounting for gender rotation, with a total of 19 public baths. I visited both on day use and as an overnight guest — the experience is very different. The hotel is large with three wings connected by long corridors, shopping arcades, restaurants, and a rough-around-the-edges vibe — essentially three hotels connected to each other with various infrastructure. The baths are also spread across the three wings.
The main way to get there is by regular ferry from Hotel Urashima Pier to the hotel. I didn't use it, but people were constantly arriving on it.
They stamp the 88 Onsen of Wakayama stamp book. They sell the 12 Onsen of Wakayama stamp book. They issue Toreco cards for the onsen, but they were out of stock during my visit. There's an internal onsen stamp rally (completing it gets you a packet of onsen salt).
A) Day use at 2500 yen. Available from 09:00 to 19:00 (last entry 18:00). On day use you can visit 6 bathing zones, but you need to time it right to hit all of them considering breaks and gender swaps. It turns into an intense onsen adventure of constantly moving between baths for 5-7 hours that fly by:
- 09:00 Boukido (version 1)
- 10:00 Takinoyu/Hamayunoyu (version 1)
- 11:00 Genbudo
- 12:00 Isonoyu
- 13:00 Boukido (version 2, after gender swap)
- 15:00 Takinoyu/Hamayunoyu (version 2, after gender swap)
The day use experience was amazing. Constantly moving between different baths, three zones with epic cave baths carved into rock, great water, various temperatures. From early morning there were very few people and only around 12-1 PM did people start showing up, still in moderate numbers.
B) For the overnight stay I booked the Sanjokan wing — rooms there are on average more expensive, more Japanese-style rooms, and only guests in this wing get access to the additional Haruomine bath. I had a tatami room with a bay view.
Booked through Trip.com with two meals — also contacted the hotel separately to confirm the meal format (turned out to be buffet by default). I paid extra to upgrade to double kaiseki. The kaiseki seemed to not be the hotel's strong suit, as the separate kaiseki dining room with many tables had only me, and while the kaiseki was generous in volume, the taste was quite average (especially the seafood).
After check-in the hotel and baths got crowded, with constant hustle and bustle, and the atmosphere suffered compared to the pre-check-in day use slot. Things started to settle back down after 9-10 PM.
C) Conclusion:
- A uniquely top-tier place with onsen in rock caves, a must-visit and a standalone reason to come to Katsuura;
- Day use is much better than staying overnight, but to fully enjoy the day use experience you need more onsen stamina and better timing;
- Overnight bonus: late evening time slots with few people, and if staying in Sanjokan — an additional bath zone;
- Might be overwhelming for beginners due to the sheer volume of onsen content;
- Probably not worth upgrading to kaiseki.
D) Onsen details in separate parts.
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653. Hotel Urashima, Nachikatsuura, Wakayama (pt.2) ★★★
D) Onsen. Judging by old photos, the cave baths used to be konyoku with no chains or fences at all, but now there's a clear gender split and barriers have appeared, though still reasonable. In the changing rooms there are notices that you might encounter bugs and they're not pests. The baths:
1. Boukido left. 05:00-10:00 men's, 13:00-23:00 women's. Water composition table is identical to Takinoyu/Hamayunoyu. Consists of two caves with high ceilings in rock, connected by a passageway where the showers are. There's a good Google Maps panorama of this area that conveys very well what it looks like in person.
1.1. Left cave. Epic view of the bay from the cave. Looks incredibly cool. Proper sulfurous onsen smell.
1.1.1. Bath at the cave edge. Depending on where you sit the view starts to fade, but the atmosphere remains incredible. Chain installed along the bath edge. Cloudy blue-white water, temperature 39. Proper sulfurous onsen smell.
1.1.2. Bath closer to the changing room. Gives a wider panorama than the edge bath, but you're still drawn to sit in the edge one. Cloudy blue-white water, temperature 41.
1.2. Right cave. Bay view. The cave is more open, feels different and also very cool. Proper sulfurous onsen smell.
1.2.1. Bath at the cave edge. Thin lattice fence. Bay view. Cloudy blue-white water, temperature 38.
1.2.2. Bath on the upper tier toward the bay. View of the cave and toward the bay. Cloudy blue-white water, temperature 40.
1.2.3. Bath on the upper tier by the wall. View of the cave and toward the bay. Cloudy blue-white water, temperature 41.5.
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653. Hotel Urashima, Nachikatsuura, Wakayama (pt.3) ★★★
D) Onsen. Baths continued:
2. Takinoyu. 06:00-12:00 men's, 15:00-24:00 women's.
2.1. Indoor room with a bath. Slightly cloudy blue-white water. Temperature 42.5. Breathing inside is fine.
2.2. A space with a roof and walls but partly outdoors. Breathing inside is good.
2.2.1. Small bath. Cloudy blue-white water, temperature 39.
2.2.2. Medium bath. Cloudy blue-white water, temperature 41.
3. Hamayunoyu. 06:00-12:00 women's, 15:00-24:00 men's.
Indoor bath. Cloudy bluish water, temperature 41. Breathing inside is comfortable.
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653. Hotel Urashima, Nachikatsuura, Wakayama (pt.4) ★★★
D) Onsen. Baths continued:
4. Genbudo. No gender swap. Consists of an elongated cave with a high ceiling in rock and an exit to a small open area. Proper sulfurous onsen smell.
4.1. Large bath inside. Cloudy blue-white water, temperature 41-42.
4.2. Small outdoor bath. View through a lattice fence of the cliff, hotel, and waves crashing on rocks. The view is very cool, but the fence does detract from it. Clear water with fine white limescale. Temperature 39-40.
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653. Hotel Urashima, Nachikatsuura, Wakayama (pt.5) ★★★
D) Onsen. Baths continued:
5. Boukido right. 05:00-10:00 women's, 13:00-23:00 men's. A cave with a high ceiling in rock with an exit to a bath closer to the bay. Cool view of the cave interior and the bay. Bath photos from the internet match. Water composition table is identical to Takinoyu/Hamayunoyu.
5.1. Main bath closer to the wall. Cloudy blue-white water, temperature 41.
5.2. Bath in a recess. Cloudy blue-white water, temperature 42.
5.3. Bath on the main tier closer to the bay. Cloudy blue-white water, temperature 42.5-43.
5.4. Bath at the cave edge. Lattice fence. View of the cave and the bay. Cloudy blue-white water, temperature 38.
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653. Hotel Urashima, Nachikatsuura, Wakayama (pt.6) ★★★
D) Onsen. Baths continued:
6. Isonoyu. No gender swap. A fairly utilitarian indoor bathing zone. Breathing inside is fine.
6.1. Large bath. Clear water, temperature 41.5.
6.2. Small bath. Clear water with a slight greenish tint. Temperature 40.
7. Haruomine. Available only for Sanjokan wing guests. No gender swap. Indoor zone with a pleasant view of the bay and town. Breathing inside is comfortable.
7.1. Large bath, cloudy bluish water, temperature 41.
7.2. Small bath, cloudy bluish water, temperature 41.
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