Nagasaki Prefecture lies in the northwestern part of Kyushu, the third-largest island of Japan and most southwesterly of its four main islands, and consists of five peninsulas and numerous islands. With the sea in between, it stands face-to-face with a continent, part of which is China, and the Korean Peninsula. It has therefore long been an important transportation point facing the continent of Asia. Ports for trade with Portugal and Holland were also established there in the 16th century. In addition, since it was once the center of Christian propagation, there are many exotic historical ruins and buildings that still remain within the prefecture.