Wilis volcano in the eastern end of Central Java is an isolated volcano with no known historic eruption, although there is a report of an eruption in 1641 AD, but most likely this was an eruption from nearby Kelut volcano. Increased fumarolic activity was reported in 1885.

Wilis was formed during three episodes dating back around 700,000 years. The most recent cone grew during the past 10,000 years. There are fumaroles and boiling mud ponds near Lake Ngebel on the lower western flank of the volcano.