If the fact that John F. Kennedy and James Joyce used to drink here doesn't impress you, then maybe the fact that 9/10 Guinness fiends (myself included) agree that you will find the best pint of Guinness in the universe here will.
Sure the place has even got its own Wikipedia page
Dark, unrenovated, No TVs, No Music, No Strawberry Dacquaris... Heaven.
Suggested by Andrew on Friday, January 11, 2008