Unzen is the name of the region in the center of the Shimabara-hanto Peninsula, Nagasaki Prefecture which belongs to the volcanic region of Mt. Unzen-dake.
Its principal peak is Mt. Fugen-dake and the area is part of Unzen-Amakusa National Park.
In 1990, Mt. Fugen-dake erupted after 198 years of silence. In addition to the volcanic activity of the region, Unzen is famous for one of the populous onsen destination.
The Unzen-onsen is on the southwest side of Mt. Unzen-dake, at 700 to 800 meters above sea level.
Sulfuric gas colors the ground red and yellow where fumes have burst forth, and more than thirty hot springs are scattered throughout the deserted landscape of Unzen.
An interesting story in the region is that missionaries were active in Shimabara in the early 17th century, and many of the local residents became Christians. However, the administrator of that time banned Christianity, and Shimabara became known for its harsh oppression of the religion.
Today visitors can visit the huge natural cauldrons of Jigokudani or Hells Valley of Mt. Fugen release billowing clouds of gases.