In former times, Yumenguan Pass (Jade Gate Pass) of Great Wall in Gansu was called Small Square City. Why was its name changed? There is an interesting story that answers this question.
Yumenguan in Gansu
One day, a caravan lost its way shortly after entering the area. The members of the caravan were anxious to get out of the area safely. While discussing their problem, a wild goose fell to the ground and caught by a kind-hearted young man, who held it gently in his arms. He decided to keep the goose with him until they got out of this strange place.
A short while later, the young man was surprised to see tears running down the face of the goose and heard it say, "Honk, honk, give me food, honk, honk, take you out". Hearing this, the young man understood that the goose fell behind its group because of hunger. So he fetched food and water and fed the goose. Having eaten enough food, the goose flew up to the sky and circled around over the caravan. The goose led the caravan safely to their destination, Small Square City.
Some time later, the caravan lost their way again at the same place. The goose flew to them and said, "Honk, honk, get lost; honk, honk, lead you out if you inlay jade on the Pass". As the goose said this, it flew over the caravan and led the caravan out of the strange area. Only the young man who had previously rescued the goose understood what the goose said. He told the leader that the goose asked them to inlay a luminous black green jade on the top of Small Square City. The rays of the jade would be able to guide caravans and no one will get lost in the dark any more. Hearing these words, the boss thought it over and then he refused to give up his valuable jade.
Unfortunately, this very same caravan got lost once again! They could not find water and were dying of thirst. Just at their bleakest moment, the goose flew to them and cried, "You are lost, inlay the jade or never get out". The young man repeated the goose's words to the caravan leader. His boss was afraid and did not know what to do. He asked the young man for help. The young man told him to kneel down and promise the goose that he would inlay the jade. The boss heeded the young man and the caravan was led out of the desolate lands to safety.
The caravan which had now been rescued three times by the goose reached the Small Square City safely. The caravan leader was no longer greedily holding on to the jade. He chose the best and largest luminous black green jade to inlay on the top of the pass. Whenever the curtain of the night fell, the brilliant rays that the jade sent out could be clearly seen from even a far distance. With this guide, caravans passing this post never got lost. From then on, the Small Square City was changed into Yumenguan Pass of Great Wall.