We had heard about the gaol previous to our trip to Ireland and decided it would be worth a visit.
As it turned out , the visit became the highlight of our 2 night stay on the island. It's difficult to walk to from the city centre as It's mostly uphill, but the 10 min taxi drive only cost us 7 Euros.
The entry fee is 8 Euros per adult with free guide book, and for additional 3 Euro, you're supplied with audio commentary via earphones (which you get to keep at the end)!
The tour itself takes around 40 mins, and is really informative. And along with the waxwork models of the prisoners and warders, you get a real atmospheric feel.
There's a gift shop attached to the wing. The staff are extremely knowledgable and friendly, and the place is well worth a visit if you're in the area.