Just over an hour's drive from Nagasaki's city center, the hot spring resort of Unzen Onsen became a popular summer resort for Nagasaki's foreign residents in the early twentieth century, for its cooler mountain climate and relaxing springs. Many of the area hotels have outdoor hot springs with views of Mt. Unzen. You can also visit the nearby Unzen Hells. These 30 or so pools of bubbling, sulfuric water and mud were once the grim setting for the deaths of Christian martyrs in the Edo period (1603-1867).