The crypts beneath the Wawel Cathedral hold the tombs of Polish kings, national heroes, generals and revolutionaries, including rulers of the Polish–Lithuanian Commonwealth such as: Jan III Sobieski and his consort Marie Casimire (Maria Kazimiera); the remains of Tadeusz Kościuszko, the leader of a Polish national insurrection and Brigadier General in the American Revolutionary War; Władysław Sikorski, Prime Minister of the Polish Government in Exile and Commander-in-Chief of the Polish Armed Forces; Marshal Józef Piłsudski, founder of the Second Polish Republic. Pope John Paul II celebrated his first mass in St. Leonard's Crypt. He considered being buried at the Wawel Cathedral also at one point in time, while some of the people of Poland had hoped that, following ancient custom, his heart would be brought there and kept alongside the remains of the great Polish rulers. (John Paul II was buried under St. Peter's Basilica, a papal burial site since antiquity, instead.)