Around the Suwanoike Pond, lava erupted about 600,000 years ago. The lava known as "Suwanoike Basalt" is distributed in this area, and the unique terrain of gentle hills created by basaltic volcanoes is widespread. On the southeastern edge of Suwanoike Pond, several steep cliffs with a height of 30-40 meters align in a southwestern direction. These criffs were created when a fault running beneath the area cut through the Suwanoike Basalt. The Suwanoike Pond is a man-made pond for irrigation, made by damming a hollow created by landslide, and it provides water for agricultural use to the downstream fields.
It is a popular fishing spot and also a good place for bird watching as many wild birds live around the pond. At Mt. Unzen Suwanoike Visitor Center, located on the shore of Suwanoike Pond, you can obtain the latest information on wildlife and observe the night sky ahd the sun using the large astronomical telescope installed in its dome. The Visitor Center also holds many events to enjoy the rich nature such as the regular event of plant dyeing and star-gazing, and serves as a core center for environmental education. The pond has also been selected as one of the top 100 reservoirs in Japan, for being a habitat for a wide variety of wildlife species.