Ookama Onsen is one of the representative hot springs of Nyuto Onsenkyo (Nyuto Hot Spring Village), located at the foot of Mount Nyuto within Towada-Hachimantai National Park in Senboku City, Akita Prefecture. The most distinctive feature of Ookama Onsen is its building, which was constructed by relocating and renovating a wooden elementary school building from elsewhere in the prefecture. The nostalgic structure exudes a retro Showa-era atmosphere. Inside the building, original school signs such as "Principal's Office," "Staff Room," and "Auditorium" remain, creating a unique time-traveling experience.

Nyuto Onsenkyo consists of seven hot spring inns, each with its own unique source spring. Ookama Onsen's source is an "acidic arsenous sodium chloride sulfate spring," characterized by its tea-brown cloudy water. The greenish-tinted water is also called "bitter spring" and has been traditionally known as the "healing water for wounds" and "water for skin." It has a slight hydrogen sulfide smell, and the source temperature ranges from 94.7 to 98°C, though it is diluted with water for temperature adjustment.

The bathing facilities consist of an outdoor bath surrounded by beech trees and an indoor bath. The outdoor section has two pools - the larger one is slightly cooler, while the smaller one offers water with more concentrated mineral content. Operating year-round with 24-hour bathing available (day-use bathing: 9:00-16:30) is a major attraction. During summer season (April 1 - October 31), a free footbath is installed at the entrance, serving as a resting spot for mountain climbers and trekking enthusiasts.

There is also a bus stop for the "Yumeguri-go" (hot spring tour bus) that circulates within Nyuto Onsenkyo, making it a convenient base for exploring all seven hot springs. By purchasing a Yumeguri-techo (hot spring tour booklet for 2,500 yen), visitors can enjoy day-use bathing at all seven Nyuto Onsenkyo hot springs, making it a popular spot among hot spring enthusiasts.

The location offers good access to nearby attractions such as Mount Akita-Komagatake and Lake Tazawa, making it a popular base for mountain climbing and sightseeing. It maintains the atmosphere of a traditional mountain lodge while offering modern comforts - a true hidden hot spring gem.