Which volcano has the longest known lava tube?

Kazumura Cave, on the slopes of Kilauea in Hawaii, is the longest known lava tube system on Earth, with surveyed passages of more than 65 km. It formed when lava flowed through underground channels and drained away, leaving a cave behind. Lava tubes like this are important for understanding volcanic eruptions and lava flow behavior. They also create unique underground ecosystems and geology.