66km (41 miles) SE of Nagasaki
Unzen Spa is a small hot-spring resort town located about 700m (2,300 ft.) above sea level in the pine-covered hills of the Shimabara Peninsula. Thanks to its high altitude, cool mountain air, great scenery, and hot sulfur springs, Unzen became popular in the 1890s as a summer resort for American and European visitors, who came from as far away as Shanghai, Hong Kong, Harbin, and Singapore to escape the oppressively humid summers. They arrived in Unzen by bamboo palanquin from Obama, 11km (6 3/4 miles) away. In 1911, Unzen became the first prefectural park in Japan. In 1934, the area became Unzen-Amakusa National Park, one of the nation's first national parks; it covers 282 sq. km (113 sq. miles).
I like Unzen Spa because it's small and navigable. It consists basically of just a few streets with hotels and ryokan spread along them, a welcome relief if you've been spending hectic weeks rushing through big cities and catching buses and trains. Hiking paths wind into the tree-covered hills, and dense clouds of steam arise from solfataras (vents) and fumaroles, evidence of volcanic activity. For visitors, the best result of all that thermal activity is the abundance of hot springs: Unzen's name derives from "Onsen," meaning "hot spring."