It happens today.
It happens every year in February - March. Millions of Lady Devotees, without any age bar or caste bar, assemble together in the city of Trivandrum, Kerala, India to pray to the Goddess Kali. They gather in the small streets, the main roads and the highways, make a fireplace out of bricks and take part in the Pongala festival. (Pongala, comes from the Tamil Word Pongal. It is rice cooked with jaggery, coconut and spices). Pongala is made as an offering to the Goddess.
In 1997, around 1.5 million devotees participated in the festival. In 2007, it became 2.7 million. That stats saw Attukal Pongala entering the Guinness Book. And this year, it is all set to break its own record.
You can read more at Attukal Pongala Blog and Temple Website.