Today the site of a fashionable (and expensive) restaurant in the hills overlooking Dublin, it was the site of a celebrated haunting back in the ’60s.
Mrs Margaret O’Brien purchased the dilapitated house in 1968 intentioned to turn it into a retreat for artists and intellectuals.

Today the site of a fashionable (and expensive) restaurant in the hills overlooking Dublin, it was the site of a celebrated haunting back in the ’60s.
Mrs Margaret O’Brien purchased the dilapitated house in 1968 intentioned to turn it into a retreat for artists and intellectuals.
The hired workers slept on the site during the much needed renovation works and soon told Mrs O’Brien that the house, as can be expected, was haunted. Mrs O’Brien attributed this rumors to an overactive imagination and paid no further attention to them, as well as rumors among the country folk about an alarmingly large black cat living in the garden. 
After the workers moved out Mrs O’Brien hired Tom McAssey, a Dublin artist, to decorate the interior. One evening McAssey had just finished his day work and set about closing down the house for the night together with two hired hands. Now, description of what happened next are much varied so I’ll stick to the one given by McAssey himself to Frank Smyth for his book Ghosts and Poltergeists.
After closing down the main entrance one of the hired hands told him that there must be something wrong with the lock because the heavy door was now open. The three men went to check the door and realized that it was open. An undistinguishable figure was outside. Thinking about a practical joke McAssey said "It won’t work, I can see you, so get in". A low voice answered back "You cannot see me, leave the door open". The two hired hands immediately took flight. McAssey was deeply frightened but decided to have a better look. A black cat, as large as a "Dalmatian dog", with amber colored eyes was sitting in vestibule. This proved too much for him and he joined his fellow workers in their scramble. A little later Tom McAssey painted a portait of this enormous cat on canvas. This painting is still in the house, greeting restaurant patrons. 
As unsettling as a large, talking cat may seem it proved to be completely harmless. Many guests saw the cats over the years and Val McGann, a sportsman turned artist, told that he tried to capture the immense and long lived feline a number of times but it always proved to be smarter and faster than him.
It has been said that two exorcism were carried out in the house, that a group of artists holding a mock sèance were scared silly by poltergeist activity or that a brass figurine of the Devil was found together with human remains under the fllor. These are modern, unsubstantiated rumors.
On Montpelier Hill, not far from Killakee House, there are the ruins of a country residence which are said to have been home of the "Irish branch" of the Hellfire Club. As I have already covered the issue before you may well understand my scepticism. Local legends say that it was the meeting point for Dublin witches and other devil worshippers and that the place was burnt down by Satan himself during a ritual.
Rathfarnham proper is home to another legend about a ghostly coach driven by a headless wraith. But we’ll cover this interesting matter soon enough.