DUBLIN (AP) — Hundreds of thousands of people packed the streets of Dublin on Monday to watch Ireland’s national St. Patrick’s Day parade, as crowds in green flooded cities and towns across the country to mark the annual holiday.

Officials said half a million spectators were expected to line the parade route in the capital to watch the colorful floats, performers and dancers. Some 4,000 people and 12 marching bands from across Ireland, North America and Austria were taking part this year to commemorate Ireland’s patron saint.

While the tradition of St. Patrick’s Day parades began in the United States in the 1700s, and the biggest parade these days takes place in New York, officials say the holiday draws some 100,000 tourists to Ireland each year.

In the U.S., boisterous celebrations in New York, Boston, elsewhere

In London, Kate, the Princess of Wales, marked the occasion with a solo visit to the Irish Guards at Wellington Barracks.

The royal, who is the ceremonial colonel of the regiment, presented fresh sprigs of shamrock and awarded medals to soldiers before the regiment’s St. Patrick’s Day parade. She enjoyed a half pint of Guinness afterward as she chatted and joked with the soldiers.

Kate, who missed the Guards’ celebrations last year after she was diagnosed with cancer, has gradually returned to public duties.