Echigo-Nagano Onsen Rankeiso is a traditional hot spring inn and member of the Japan Secret Hot Springs Association, nestled along the Monzen River in Sanjo City, Niigata Prefecture. Designated as a Registered Tangible Cultural Property of Japan, it features historic and charming buildings. The inn consists of three buildings: 'Ryokufu-kan' (main hall), 'Keiryukan' (stream-view building), and 'Suiyukan' (water-play building), with 17 guest rooms total. It's a quiet secluded hot spring in a mountain valley, surrounded by cherry and ginkgo trees in a nature-rich environment.

The hot spring is a sodium-chloride cold mineral spring (hypertonic weakly alkaline cold mineral spring) with a source temperature of approximately 16°C and pH 7.6. Despite being located in the mountains, it's known as a 'salty hot spring' with strong salt content, containing components similar to seawater. It's said to be effective for cuts, burns, sensitivity to cold, gynecological issues, neuralgia, and heat rash. As the source is a cold mineral spring, it's heated, but carefully managed to preserve the source components.

The bathing facilities include 4 indoor baths and 4 outdoor baths, totaling 8 different baths, each with its own unique character. Notable features include Goemon-style outdoor baths and other distinctive bathtubs. With a history as a therapeutic spring, many people visit for hot spring therapy of this 'strong salt cold mineral spring.'

The facility is equipped with Wi-Fi, TV, yukata, hairdryer, and other amenities, and is barrier-free accessible (wheelchair accessible). Meals feature mountain village cuisine using local wild vegetables and river fish, with seasonal dishes highlighting regional ingredients. Dishes prepared with water from the Gozu mountain system are deeply nourishing and healing, complementing the hot spring experience.

Accommodation rates are 17,750-27,650 yen per person per night with two meals (tax included). Day-use bathing is available for 1,000 yen for adults and 700 yen for children, with operating hours from 11:00-14:30. Check-in is at 15:00, check-out at 10:00, and the inn is open year-round.

Access is by car from JR Shinetsu Main Line Higashi-Sanjo Station (about 40 minutes) or from JR Banetsu West Line Kamo Station (about 35 minutes). By car, it's about 40 minutes from Sanjo-Tsubame IC on the Hokuriku Expressway. Free parking is available. Activities such as rafting (Ikarashi River), cycling, yoga, and workation are offered, making it a hot spring inn where you can refresh in nature.