Most people land in Bali and stay there. The volcanoes are a ferry ride west, and they are worth planning a route around rather than bolting a day trip onto a beach holiday.
Indonesia is more than 17,000 islands along the equator, with a line of volcanoes running through them. On Java a few are always letting off steam.
Next door, Bali has rice terraces and a temple in almost every village. Java itself is home to more than half of all Indonesians.
We call you, then send a plan on paper, day by day, and a few Finds to build the trip around. Whether or not you book.