Boudhnath Stupa
Also called Khasti, one 
of the largest Buddhist stupa in the world lies 6 km to the east of the city. The unique highlight of this great Buddhist monument is that, it is set in the octagonal Mandala design; with the niche around are the hundreds of prayer wheels & the 108 images of Buddha adorning the stupa. This also has about four dozens of monasteries in its vicinity.