Durga puja is the most prominent festival of Bengalis and Calcutta turns a new city during the last four days of the festival from Maha-Shashti (the sixth day), the day of Bodhon on Maha-Shashti to the day when the idols are immersed in the rivers, lakes and seas on the evening of Dashami. However, it is considered to immerse the idols in the sacred waters of the River Ganges. It is believed that the Mother Goddess descends to the Earth on Shashthi and returns to her abode on Dashmi. The fresh and cool air of the pleasant winters, the clear skies, mildly fragrant Shiuli (a type of flower), the bountiful harvest in the fields and chanting of mantras and shlokas to worship Shakti, all collectively set up the scene for the ten-day long festival of Durga Puja. The preparations are done long before the festival to clean and decorate homes, buy gifts for fiends and relatives and new clothes for the celebrations and prepare mouth-watering delicacies for the occasion.