I couldn't have been more wrong.
Kilmainham Gaol was built in 1796 and has a long, troubled history. What it is most known for, however, is being home to the executions of the rebels of the Easter Rising in 1916.
Before I get into all of that though, there are quite a few years to cover.
In 1796 Kilmainham was built, officially named the "County of Dublin Gaol," and often called the "New Gaol" by the people of Dublin, as it replaced the old gaol that had been located just next to it. At the old gaol, prisoners were held together in one cell, regardless of crime, age, or gender. It was eventually noticed that just throwing all of the criminals in one room for a certain amount of time was not helping stop crime. If anything, prisoners were exchanging skills, and people would learn new criminal behavior to survive in jail. Kilmainham was built in response to this, and a the time it was built, it was the most modern prison in the world.
What really turned the public eye to Kilmainham Gaol though, was not how it was housing these prisoners, but how they were executing them.
The 1916 rebellion was not a popular one, and, originally, when General Maxwell began executing the political leaders, the public was not terribly shocked. As time went on and Maxwell kept executing prisoners that were more or less involved, the people's feelings were stirred.
William Pearsse, for instance, was the younger brother of Patrick Pearse, a rebel leader. He was barely part of the rising at all, and was known and liked throughout Dublin as a gentle artist. When he was executed, because of his relation to Patrick Pearse, citizens began to question General Maxwell. Joseph Plunkett, despite being one of the leaders of the rising, also stirred the hearts of the dubliners. Twenty-eight years old, he asked for permission to marry his fiance Grace Gifford before his execution, and was awarded it. The two were married in the Kilmainham Chapel, and were allotted ten minutes of time together (with two armed guards present) before Plunkett was executed. This story of the young newlyweds also created sympathy for the rebels. By this time, King George had realized that these executions were going to turn the Irish people against him, and asked Maxwell to stop. The General disregarded him, however, and continued to execute the people he felt were involved with the rebellion. the last leader to be executed was James Connolly. His leg had been badly injured during the Rising, and he couldn't walk due to the gangrene that had set in. He was executed strapped to a chair, and the people of Dublin were horrified.
From here on, the general public opinion switched to be more in favor of the Irish nationalists, and many historians believe that it was these executions that turned the tide of Irish history.
I would definitely recommend touring the Kilmainham Gaol to anyone seeking a deeper understanding of the 1916 Easter Rising.