St. Patrick was the first Christian missionary in Ireland and is considered the country's patron saint. St. Patrick's Day is a public holiday in the Republic of Ireland, Northern Ireland, Montserrat, and the Canadian province of Newfoundland and Labrador. These days, St. Patrick's Day is celebrated in many different places across the world.

Born Maewyn Succat, Ireland's patron saint is presumed to have lived in the fifth century and was a Briton. It's said he was taken to Ireland as a slave. There he found his way to Christianity. He later managed to reach France on a ship and studied theology there. Back in England he was ordained a priest, taking the name Patrick. Following a vision, he began to convert Celtic pagans in Ireland.

People celebrating St. Patrick's Day traditionally wear green. Some sport imaginative costumes and paint their faces. Originally the color associated with St. Patrick was blue. During the Irish rebellion of 1798, however, green became the color that symbolized national identity — and remains so to this day.

According to legend St. Patrick is said to have used shamrocks to illustrate the Holy Trinity of Father, Son and Holy Ghost to Irish polytheists. Even though the man in the picture has five-leaf clovers over his eyes and many people sport four-leaf clovers on St. Patrick's day — the Irish national symbol has just three.

St. Patrick's Day is a public holiday in Ireland. There are parades and processions, church services and folk dancing, as here in Dublin. But Ireland isn't the only place where St. Patrick's Day is celebrated, because emigrants from Ireland and their descendants also take this day very seriously.

St. Patrick's Day is especially popular in the United States. That's not surprising, because the country is home to some 34 million people with Irish roots! The first parade took place in 1843 in Chicago, and the city pulls out all the stops on St. Patrick's Day. Even the Chicago River is dyed green, this year already on March 11.

Every year, St. Patrick's Day grows more popular abroad. Many famous landmarks are illuminated in green to mark the occasion, among them the Sydney Opera House also the Leaning Tower of Pisa.

Munich is home to one of the biggest St. Patrick's day parades on the European continent. Participants march from the square known as Münchner Freiheit, over Leopoldstrasse and Ludwigstrasse, to Odeonsplatz. There, people celebrate with Celtic and Irish rock and traditional folk music.

On St. Patrick's Day people dye all kinds of things green: their hair, clothing and even beer. Generally, beer consumption around St. Patrick's Day increases enormously — especially that of Irish stout.

People used to simply wave Irish flags but now there is an entire industry that supplies St. Paddy's day party paraphernalia. Some are calling for things to be toned down a bit, though that seems unlikely. St. Patrick's Day has simply become too popular.