For generations of literary tourists it has proved a puzzle as time-consuming and challenging as reading the book in which it was originally set.
In Ulysses, the author James Joyce defies readers to cross Dublin without passing one of its 1,000 pubs. The debate has raged in saloon bars and snugs on the banks of the Liffey ever since being laid down in the sprawling 1922 masterpiece.
The software developer Rory McCann has now put an end to the black-stuff-fuelled arguments after more than a year of trying to find a hi-tech solution. Despite never having read the book, and with little more than a passing interest in his city's most celebrated writer, he has worked out how to complete the alcohol-free odyssey with the help of a computer algorithm and an online map.
"You always hear that it's not possible to cross the city without running into a pub, and I thought with modern computers maybe we could look into it again," he said.
The map was published to coincide with the annual Bloomsday yesterday, in which Joyce fans recreate a day in the life of the book's protagonist, Leopold Bloom, and has already sparked much debate. One hot topic is whether it is in the spirit of the challenge to skirt the length of the Guinness brewery at St James' Gate, or to pass modern establishments where suitable refreshment could be on offer.
Mr McCann said: "Some people are a bit annoyed that I have ruined a perfectly good argument that they can have in the pub. I feel it is pretty watertight now and two people have already cycled it and said it works."