The Keya Otono cave is formed from columnar jointed basalt, created by volcanic cooling processes.
The cave entrance measures approximately 64 meters in height.
The site is part of the Genkai Quasi-National Park.
The boat tour has been in operation for decades, traditionally managed by local fishermen.
Keya Oton Kankousha serves as the primary ticket office for boat tours to Keya Otono, a massive basalt sea cave located on the Itoshima Peninsula. The cave is officially designated as a National Natural Monument and is recognized as one of Japan's three major basalt caves. Tours operate using small fishing-style boats to navigate the narrow entrance of the cave, which features a hexagonal columnar jointing structure. The boat tour relies on favorable sea conditions to access the cave interior. The office is situated within the Keya Beach area, providing a direct gateway to the coastline's geological features.
From the bow of the boat as it enters the cave, capturing the vertical basalt columns against the interior water.
Check the official website or call ahead on the morning of your visit, as tours are frequently canceled due to high waves or strong winds.
Wear sensible, non-slip footwear as the pier and boat decks can be wet or unstable.
Bring light rain protection or a windbreaker, even on sunny days, due to sea spray.
Do not attempt to swim near the cave entrance due to dangerous currents and underwater rock formations.
Tours operate seasonally from spring through autumn and are suspended during winter months; operations are highly weather-dependent and may be canceled daily.
Life jackets are mandatory for all passengers; follow instructions from boat operators regarding seating and safety.
