The peninsula incorporates the cities of Shimabara, Minamishimabara, and Unzen.

The northern, eastern, and southeastern coasts of the peninsula face the Ariake Sea, and the western coast faces Tachibana Bay.

An active group of volcanoes known collectively as Mount Unzen lies in the middle of the peninsula, with many hot springs, such as Unzen Onsen and the extremely hot Obama Onsen.

The peninsula was also the site of the Shimabara Rebellion, a 1637–1638 peasant and rōnin revolt, led by Christians.

This further reinforced distrust of Christians and foreigners by Shōgun Iemitsu and contributed to the 1639 decision to isolate Japan from the outside world.