A Haven of Peace and Happiness

Tao Yuanming, a famous writer of the Eastern Jin Dynasty (317-420), wrote the well-known essay Peach-Blossom Spring. In it he tells a story which goes like this: A fisherman happened to come upon a place called Peach-Blossom Spring. Squeezing through a cave, he found a village, the residents of which were descendants of refugees from the Qin Dynasty. It was a paradise isolated from the outside world, without exploitation or oppression, and everybody living and working in peace and contentment. The fisherman left the villagers and went home. But he could never find the place again. 

东晋的文学家陶渊明写了一片著名的文章叫《桃花源记》。叙述一个渔人出外捕鱼的时候，偶然来到了桃花源这个地方。从这里通过一个山洞，发现了一个村子，这里的居民是秦朝时避难人的后代。这是一个与世隔绝、没有剥削和压迫、人人安居乐业的美好社会。渔人告别村民回家以后，再也找不到这个地方了。 

This idiom is derived from the above story, and is used to mean an isolated, ideal world.

后来，由这个故事产生了“世外桃源”这个成语，用来比喻与世隔绝的、理想的美好世界。