Experience the Tihar Festival in Nepal (aka the Festival of Lights). The timing of the festival changes every year - it officially is celebrated in five days starting from the thirteenth day of the waning moon in October. Basically this means that if you are in Nepal in October - then you'll probably experience it!
Throughout Nepal many candles are lit inside and outside the house giving the whole country a soft glow. Tihar is a 5 day festival that celebrates the relationship of brothers and sisters, the gods, and animals (dogs, crows, and cows). Each day has a special meaning and custom.
I was lucky enough to be trekking through small villages on the Annapurna circuit during the 5 days of the festival and was able to experience how the small village communities celebrated.