Its one of traditional way of celebrating Bhogali bihu by the people of assam . The Bhogali bihu or Magh bihu celebrated in the 1st day of the assamese month Magh(ie January 14-16).The cone like structure is called Bhelaghor which is made of Rice plant stem(lower stem) which is called Nara in Assamese. One or two people usually lit up the structure after worshiping to god....The bhelaghor is built for warming the people in the coldest morning(the Bihu day)