Pope John XXIII:

Far from being a mere "stopgap" pope, to great excitement, John XXIII called for an ecumenical council fewer than ninety years after the First Vatican Council (Vatican I's predecessor, the Council of Trent, had been held in the 16th century). This decision was announced on 29 January 1959 at the Basilica of Saint Paul Outside the Walls. Cardinal Giovanni Battista Montini, who later became Pope Paul VI, remarked to Giulio Bevilacqua that "this holy old boy doesn't realise what a hornet's nest he's stirring up". From the Second Vatican Council came changes that reshaped the face of Catholicism: a comprehensively revised liturgy, a stronger emphasis on ecumenism, and a new approach to the world.

Please answer a question about this article. If the question is unanswerable, say "unanswerable". Where was the decision made for this council?
the Basilica of Saint Paul Outside the Walls