Paddy's Day is the biggest holiday in Ireland and there are festivities all over the country.
Here in Dublin, even though there are lots of things going on, the most popular attraction is the parade that starts at Parnell Square and ends at St. Patrick's Cathedral. People from all over the world take part and you see tons of people dressed in green. The parade lasts about 2 hours. Afterwards people go for some paints.
(By the way, "emerald isle" is an American thing lol)
Americans refer to Ireland as "Emerald Isle" but people don't really say it here