Bernadette to eat grass, and drink of, and wash herself in, the muddy waters of what was to become the miraculous healing spring of Lourdes. When Bernadette stood up and turned around, she was unrecognizable to the crowd, which became scandalized at her “bizarre” behavior. Heaven put Bernadette to a test of humility—as it does for all of us—to remind us of our utter misery and nothingness without God's grace.

Our Lady at Pontmain, France
This apparition occurred on the evening of January 17, 1871, during the Franco-Prussian War. For several hours Mary appeared in Heaven wearing a dark blue dress with a crucifix in her hands. Below the apparition appeared the words, “Please pray. God will hear you soon. My Son lets Himself be touched.” A few days later, the French-German armistice was signed.

Apocalyptic tableau at Knock, Ireland
In 1879, Our Lady, St. Joseph, and St. John the Evangelist appeared on the side of a church, in a blaze of light, with an altar and a lamb and a cross. This seemed to indicate that the unfolding of the Apocalypse was about to begin.

Apparitions of Rue du Bac, Paris
The story of modern apparitions really begins with the Virgin Mary appearing to a young novice, Catherine Labouré, in a convent chapel in Paris in 1830. Our Lady there gave the world through Catherine the “Miraculous Medal,” which was to flood the Earth with a superabundance of graces.

Appearances at La Salette, France
In 1846, the Virgin Mary appeared to two children, Melanie Calvat, aged 14, and Maximin Giraud, aged 11, on a mountain in the French Alps. Our Lady gave them a Message in common (Our Lady told them of evils threatening Her people, especially because of blasphemy and the profanation of Sunday), and then added a secret Message for each one. You read Melanie's secret at The Apparitions of Our Lady of La Salette in 1846, France.

The Virgin Mary at Lourdes, France
Next, Our Lady chooses a humble 14 year old girl named Bernadette Soubirous from an obscure town named Lourdes at the foot of the Pyrenee Mountains in southern France, near the Spanish border. In a series of apparitions spanning six months in 1858, the Virgin Mary taught the world the value of prayer, penance, poverty, and humility. The Vision asked

Our Lady at Fatima, Portugal
In 1917, the Virgin Mary appeared to three shepherd children, and She gave them three secrets: 1) A vision of Hell 2) That World War I would soon end, but a worse war would break out under the Pontificate of Pius XI, if people didn't amend their lives. She also announced that She would come to ask for the Consecration of Russia to Her Immaculate Heart and the communion of reparation on the First Saturdays. If Her requests went unheeded, Russia would spread its errors throughout the world, promoting wars and persecution of the Church.
You can get some details of the 3rd Secret at Fatima's Third Secret.

Apparitions at Garabandal, Spain
Our Lady appeared to 4 children in the little village of Garabandal. It was here that She first announced three great events: 1) The Great Warning; 2) The Great Miracle; 3) The Great Chastisement.

Our Lady comes to Bayside, New York
The Virgin Mary confirms the 3 great events at Garabandal, but adds that the Chastisement is in two parts: 1) World War 3; 2)The world will be comet-struck; and only one-quarter of mankind will survive. This will be followed by the period of Peace, as promised by Our Lady of Fatima.