Traditionally, the residents of Vrindavan including Nanda Maharaj and all the cowherd men would annually worshipped Indra, the King of Heaven, who is responsible for supplying water.
However, Krishna convinced his father to forgo the sacrifice to Indra and instead worship Govardhan Hill. He explained to his father Nanda Maharaj “This cosmic manifestation is going on under the influence of three modes of material nature—goodness, passion and ignorance. These three modes are the causes of creation, maintenance and destruction. The cloud is caused by the action of the mode of passion; therefore it is the mode of passion which causes the rainfall. And after the rainfall, the living entities derive the result—success in agricultural work. What, then, has Indra to do in this affair? Even if you do not please Indra, what can he do? We do not derive any special benefit from Indra. Even if he is there, he pours water on the ocean also, where there is no need of water. So he is pouring water on the ocean or on the land; it does not depend on our worshiping him. As far as we are concerned, we do not need to go to another city or village or foreign country. There are palatial buildings in the cities, but we are satisfied living in this forest of Vrindavan. Our specific relationship is with Govardhana Hill and Vrindavan forest and nothing more. I therefore request you, My dear father, to begin a sacrifice which will satisfy the local brahmanas and Govardhana Hill, and let us have nothing to do with Indra.”
Krishna thereafter instructed Nanda Maharaj to proceed with the Govardhan puja by preparing various foodstuffs to offer to Govardhan, give charity to brahmanas and decorate the cows and feed them. The ceremony of offering various foodstuffs to the Govardhan is also called Annakuta festival.
ISKCON temples across the world celebrate Govardhan puja annually by decorating and worshipping mountains of foodstuff which symbolize Govardhan mountain.