By Michael McKenna:

Dunlop Oriel House – Corner of Fenian Street & Westland Row, Dublin.
I had a tour around the infamous Oriel House, headquarters of the CID during the Civil War this morning. I took these pictures in the upper floor of the old Dunlop Factory at the back of the building. The iron gate over the door to the factory dates back to at least Civil War days, and probably older as I believe the building was also used to house prisoners by the British. According to the security guard who took me around the building there were still cages there as recently as 5 or 6 years ago. As Eunan O’Halpin put it “Oriel House succeeded in its task of suppressing small scale republican activities in the Dublin area, not by the sophistication and efficiency its intelligence work… but by the more direct method of striking terror into its opponents”. It was certainly quite chilling to be taken through the basement of the building. For more information on the activities of the CID, this article is quite comprehensive.

http://en.wikipedia.org/wiki/Free_State_Intelligence_Department_–_Oriel_House

Towards the end of the Civil War the CID et al actually moved out of Oriel House (whichever one it might be) and into a building on Merrion Square, close to Government Buildings. The front wall of Oriel House was blown in by a large mine. The corner building shows no sign of this, however the stone facade on the building now occupied by the RIAM looks newer than the rest of the building. I think the weight of evidence would tend towards the corner building, which also has the postal address of ‘Dunlop Oriel House’