A colouful procession depicting the rich cultural heritage of Kerala marked the Atham procession held at Thripunithura this morning, marking the beginning of Onam festivities in the state. Caparisoned elephants, tableaux, floats, folk dancers and drummers in colourful costumes marched through the streets, where thousands lined up to witness the annual event.Earlier, Kerala Assembly Speaker G Karthikeyan inaugurated the Atham procession.