On May 13, 1917, three children were pasturing their little flock in the Cova da Iria, parish of Fatima, town of Vila Nova de Ourém. today the diocese of Leiria-Fatima. They were called: Lucia de Jesus, aged 10, and her cousins Francisco and Jacinta Marto, aged 9 and 7.
About midday, after praying the Rosary, as was their custom, they were amusing themselves building a little house of stones scattered around he place where the Basilica now stands. Suddenly they saw a brilliant light, and thinking it to be lightning, they decided to go home. But as they went down the slope another flash lit up the place, and they saw on the top of a holmoak (where the Chapel of Apparitions now stands), “a Lady more brilliant than the sun”, from whose hands hung a white rosary.
The Lady told the three little shepherds that it was necessary to pray much, and she invited them to return to the Cova da Iria during five consecutive months, on the 13th day at that hour. The children did so and the 13th day of June, July, September and October, the Lady appeared to them again and spoke to them in the Cova da 0a. On the 19th of August, the apparition took place at Valinhos, about 500 meters from Aljustrel, because on the 13th the children had been carried off by the local Administrator to Vila Nova de Ourém.
At the last apparition, on October 13, with about 70,000 people present, the Lady said to them that she was the “Lady of the Rosary” and that a chapel was to be built there in her honor. After the apparition all present witnessed the miracle promised to the three children in July and September :the sun, resembling a silver disc, could be gazed at without difficulty and, whirling on itself like a wheel of fire, it seemed about to fall upon the earth.
Afterwards, when Lucia was a Religious Sister of Saint Dorothy, Our Lady appeared to her again in Spain (10 December 1925 and 15 February 1926, in the Convent of Pontevedra, and on the night of 13/14 June 1929, in the Convent of Tuy), requesting the devotion of the five first Saturdays (to pray the Rosary, meditate on the mysteries of the Rosary, confess and receive Holy Communion, in reparation for the sins committed against the Immaculate Heart of Mary), and the Consecration of Russia to the same Immaculate Heart, This request had been announced by the Apparition on 13 July 1917, in what is called the “Secret of Fatima”.
Years later, Sr. Lucia related that, between April and October of 1916, an Angel had appeared to the three seers on three occasions, twice in the Cabeço and once at the well in the garden behind Lucia´s house, who exhorted them to prayer and penance.
Since 1917 pilgrims have not ceased to come to the Cova da Iria in thousands upon thousands from all parts of the world, at first on the 13th of each month. later during the summer and winter holidays, and now more and more at weekends and any day all the year round.
More information can be found here.