The Chancellery Detention Center was a prison facility used by the National Socialist Party of the planet Ekos to detain and interrogate those suspected of committing crimes against them, or simply for being a Zeon. It was located within the Ekosian Chancellery.
In 2268, Isak was being held there when James Kirk and Spock were brought there after attempting to enter the Chancellery disguised as Nazi soldiers. They were attempting to meet with John Gill, who the Ekosians knew as their Führer, in an attempt to learn how the situation on Ekos developed. The Ekosian major responsible for interrogating them tortured and accused them of attempting to assassinate the Führer and threatened to execute them. After being ordered held by Nazi Party Chairman Eneg, Kirk and Spock escaped the detention facility using a rubindium-based laser, and brought Isak with them to a hideout being used by the resistance opposed to the regime. (TOS: "Patterns of Force")