The greatest stupa- BauddhaNath has an intersting history, Jadzima- a mother, who had a poor family used to look after her chickens, wanted to build an stupa and offer to Buddha. As she was poor she doesn't have a land so she asked land to the king of Nepal. Usually, that king wouldn't allow such activity but his words slipped out of the mouth and gave her permission to build the stupa with the word "it can be done"; maybe it was due to her karma, because of which it is also known as "Jarung Kashor Chörten" where Jarung stands for "it can be done", kashor has the meaning of "Slipped out of the mouth" and Chörten stands for stupa.
Her four sons completed the stupa because she died after she made a vase of the stupa. For the completion of the stupa, it took seven years. While constructing stupa there was drought in the country because of which they used to collect the morning dew, lying cloth outside all the night and the dew was used for mortar.
After the completion of the stupa, the four sons made a prayers where each of them made a wish. The first one made a wish to become the  Dharma king in Tibet, second one wished to become minister and help his brother, third one wished to become the abbot (head of the monks) and the last one wished to be yogi so that he can help in the obstacle to spread dharma in Tibet. During their pray, all the bodhisattvas, god, goddesses and buddhas absorbed into the stupa and gave their blessing because of which Boudhanath is also known as "All-Encompassing".
There was reborn of four brothers and their wish were fulfilled. The first brother was born as spiritual king in the Tibet "Songtsen Gampo", second brother was born as the minister of Tibet in the Songtsen Gampo kingdom "Padma Gungtsen", third brother was born as abbot "Shantarakshita" and fourth brother was born as  guru "Padmasambhava".
It is believed that Boudhanath is the main root of the Buddhism which represents the spiritual power of Buddhas and Bodhisattvas so, anyone who makes wishes to Bouddhanath stupa are fulfilled. Everybody pray whenever they see the Boudhanath stupa, even from the airplane. One of the fact of Boudhanath is while looking from the airplane Boudhanath stupa looks like a mandala.