In 1845, he partnered with Victor Baltard, who had been working for two years on the proposed new central market, Les Halles. After the first plan was presented in 1848, the two architects accepted a new project, whose works commenced in 1851. Their part of an outdoor stone structure bearing a type of metal frame in the style of Polonceau however was quickly criticised, by Hector Horeau, who called for a project that did not hide the metal, and by those who scoffed at the massive aspect of this "Fortress Halles". Work stopped in 1853 and the first pavilion was finally dismantled in 1866. A new project more in line with the wishes of the administration, with visible metal structures and simple brick fillings instead of stone façades, was proposed by the two architects between the end of 1853 and the beginning of 1854. The first two pavilions (demolished in 1972) were inaugurated in October 1857, three years after the death of Callet, Baltard continuing the work until 1874.
