Inside the pub that claims to be the oldest in Ireland, established in 900 A.D.

Established in 900 A.D., Sean's Bar claims to be the oldest pub in Ireland.

The historic bar is located in the town of Athlone, roughly halfway between Dublin and Galway.

In 2000, it was accepted as a record for the oldest pub in Ireland by the "Guinness World Records," according to a letter the organisation sent to the pub.

Today, Sean's Bar has become popular with tourists who come to try the pub's renowned Irish coffee or a pint of Guinness, and watch performances of traditional Irish music.

"The pub itself hasn't changed at all over the years," Declan Delaney, the manager of Sean's Bar, told Business Insider over email. "The building is a protected structure so any alteration to the main bar is forbidden."

Sean's has even been frequented by celebrities, including actors Mia Farrow, John C. Reilly, and Ray Meagher (known for playing Alf on the Australian TV soap "Home and Away"), who poured himself a pint on his visit in 2015.

"Rumour has it that Boy George owned the pub for a short while," Delaney said. "He was apparently good friends with the old owner of Sean's, Sean Fitzsimmons."

In the lead up to St. Patrick's Day on March 17, Business Insider spoke to Delaney to find out more about the pub's history.

Take a look inside the pub below.