Swayambhu stupa is very interesting. It is often said that the Buddha in his deathbed asked his followers to build stupas to in his memory, which means, the Stupa acrhitecture was around before the Buddha. However, the Stupa of Swayambhu (the one that evolved itself) as we see it today, is much much later than the Buddha. Probbaly his dic siples built a small monument or a stupa that "probably" contained the buddha's asthu dhatu. But later it was expanded and enlarged by the Lichhavi and the Malla rulers of the valley. The Manjushree myth is also very interesting. When Buddhism developed into a complex religion after the death of the Buddha, to give a mystical aura to it, people came up with myths such as of that of the Dhyani Buddhas (amitava et.al) and the future Buddhas (maitreya). And suddenly Buddhism had its own pantheon of deities. It also had deities similar to the Hindu deities, for example, Bhairavs (samvaras) and many more. This invention of new gods and myths surrounding them helped in institutionalizing the religion and to rival Hindusim, and which resulted in complex rituals surrounding these deities. If you think about it, it happens with every religions, they all survive on myths and rituals. The manjushree myth was probbaly added many years after the Buddha to explain the creation of the valley to rival the existing or contemporary Hindu myth regarding the valley which is quite similar to the Manjushree myth. yo sabai mero bichar ma....from the stuff i heard and read when i was young. I could be mistaken.. so feel free to correct me.