Third time lucky, due to never remembering to check the opening hours - finally the Old Royal Oak is open when I drop past. I've passed it open on other occasions, either when it was rammed due to a gig in Kilmainham; or I've been driving (usually due to working at a gig in Kilmainham!)
From one side, the pub is a relic of the pubs of Dublin of centuries ago, and from another vantage point - say
looking down, or climbing up, the stepped laneway from the River Camac it could be a corner bar in Porto, Tallinn or any other European Old Town.
The pub is a lot younger than it actually appears - it "only" dates to 1839! Its very English name presumably comes from its connection to the original customer base - the staff of the Royal Hospital which has since become IMMA.
There were actually at least two other pubs named the Royal Oak in Dublin in recent memory - one on the North Road in Finglas, which I believe is
still an empty site; and another at Heuston Station which was demolished, replaced by the Sadlers Inn pub/hotel; and is now the First Ireland Insurance offices.
The pub is on the small side, but outside of gig nights you should be able to squeeze in somewhere, and its definitely worth the bit of a trip out of the city centre if that is where you usually limit yourself to.