Around one million Hindus will flock to Kathmandu's Pashupatinath temple to observe the annual Maha Shivaratri, or "Great night of Shiva", to honour Lord Shiva, one of Hinduism's three main gods.
The pilgrimage is made by Hindus, mainly from South Asia and the world, to cleanse their sins and pray to Lord Shiva, fast, meditate and earn a place in heaven. Maha Shivarathri will be observed on February 24 this year.
One legend says that when Lord Shiva's consort, Goddess Parvati died, he emerged from the forests near the temple, his body smeared with ash and smoking cannabis.
Cannabis grows wild in the forests of Nepal, but the usage and traffic of the narcotic is illegal in the country, and only permitted as a religious ritual for ascetics during the festival, in imitatation of Lord Shiva.
The Sadhus are allowed to smoke cannabis but not sell or distribute it among pilgrims.
This year's festival include modern touches such as CCTV cameras to help protect crowds. Some of the holy men also play music on their mobile phones.
For pilgrims, the rituals also involve pouring milk on a stone statue and making offerings of fruit, sandalwood paste and incense sticks.
But for most observers, the pilgrimage remains deeply spiritual.