Diwali celebrates Rama's home coming. One of the largest Indian festivals, it's celebrated around the world by India's diaspora of Hindus, Sikhs and Buddhists. People decorate their houses with flowers, rangoli (colorful patterns created in entrances and courtyards), distribute sweets, gifts, light lamps and candles, and light fire crackers. For years, environmentalists have raised concerns over the air pollution during the festival. The large scale burning of fire crackers produces high levels of carbon dioxide, leaving behind a trail of smog for days. This year, however, the Indian government banned the use of fireworks a week before the festival.