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Built in 1882 by architect Francesco Fontana at the behest of Pope Leo XIII, it is located on the square that bears the name of the Pontiff. In neoclassical style, it has three entrances with a tetrastyle portico topped by a pediment: the interior is a basilica structure with three naves and a barrel vault, supported by Corinthian columns on which rests the blacony for women.

On the sides of the aisles are four chapels with altarpieces by Perugia painters. On the main altar is the marble Pietà by Sosnowski and in the rotunda stands the Madonna of the Rosary, with the titled saints (St. Leo the Great and St. Nicholas) and devotionals of the Pope (St. Joseph and St. Joachim).