What Happens
On Holi day people throw coloured powder (abir) and coloured water at each other, in the street, without asking. Water balloons — lola — come off balconies and rooftops onto anyone below, thrown by children who have been stockpiling for days. Around Kathmandu Durbar Square and through Thamel, dance circles form in the open with sound systems set up by whoever has one, and the crowd is a mix of Nepali families, young people from across the city, and visitors.
The Suspension of Rules
The distinctive thing about Holi is social rather than visual. For one day the ordinary constraints on who may approach, touch, or smear colour on whom are lifted — across age, caste, gender and status, in a society where those lines are usually observed. That inversion is the festival's real content, and it is what makes it exhilarating and, for some people, uncomfortable. The licence is temporary and everybody knows it; the ordinary order resumes the next morning.
Two Days, Two Regions
Nepal does not celebrate on a single day. Communities in the Terai and the lowlands play on the full moon day, and the Kathmandu Valley and the hills play the day after. A traveller moving between the two can catch both; a traveller assuming one date for the whole country will miss one of them.
Practical Warnings
Wear clothes you will throw away — powder does not fully wash out, and some of what is sold is harsh on skin and worse in eyes. Waterproof a phone or leave it behind. Expect to be soaked and coloured within minutes of stepping out; there is no version of being present and staying clean. Women travelling alone have reported groping under cover of the crowd, which is a known problem on Holi rather than an unlucky exception — going in a group, keeping to the more open squares, and leaving before the afternoon are the ordinary precautions. Note too that bhang — a cannabis preparation — circulates freely in lassi at Basantapur on the day, and is not always offered with a warning. Ask what is in a drink before accepting it.
Related Places & Sites

Characters
Rituals & Ceremonies
Part of Holi (Fagu Purnima)