The lake is classified as a maar, a broad, low-relief volcanic crater caused by a phreatomagmatic eruption.
The name 'Ippeki' translates to 'one eye,' reflecting the lake's solitary, circular appearance in the landscape.
It is a popular location for birdwatching, as the surrounding woodland acts as a migratory stop for various species.
The lake bed consists of thick volcanic ash deposits accumulated during its formation millennia ago.
Lake Ippeki is a volcanic crater lake situated in the eastern highlands of the Izu Peninsula. Known as the 'Eye of Izu,' the lake occupies a maar-type volcanic depression formed approximately 100,000 years ago. The perimeter of the lake measures roughly 4 kilometers and is surrounded by a dense forest of cedar and deciduous trees. A walking trail encircles the entire lake, providing views of Mount Omuro and the surrounding caldera landscape. The area is notable for its seasonal transitions, shifting from vibrant cherry blossoms in spring to deep autumn foliage. Freshwater fishing is permitted in designated areas, with the lake stocked primarily with bass and crucian carp. The lake’s calm, reflective surface is a focal point of the Izu-Hakone region's geological heritage.
The wooden jetty and viewing area near the main entrance.
Wear comfortable, sturdy walking shoes to navigate the unpaved sections of the lakeside path.
Bring insect repellent, especially during the summer and humid early autumn months.
Plan to visit on a weekday to avoid congestion with local weekend hikers.
Attempting to swim in the lake, as it is primarily managed for conservation and fishing, not recreation.
Respect local fishing regulations and pack out all trash to maintain the protected environmental area.
