It was a kilometer high government edifice which was noted for the statelines of its architecture as well as its grandiose chambers. There was a clean elegance of the design with vaulted rooms that were spacious and conveyed the impression of urban life and that of power. This grandeur contrasted the structure to the rough streets of the city.
In 2368, Ambassador Spock and Senator Pardek climbed through the chambers of the Irnilt in order to meet Proconsul Neral to discuss the possibility of Reunification between the Romulan and Vulcan races. After the Romulan Star Empire deception was discovered, Captain Jean-Luc Picard along with Spock and Lieutenant Commander Data were detained at the Irnilt. They later managed to free themselves and escaped from the building. (TNG novel: Unification)