The First City of the Klingon Empire was the capital city of the Klingon Empire. Located on the planet Qo'noS, it was home to the Great Hall, where the Klingon High Council met.
The city itself was divided into quarters, one of which was the Old Quarter, where Kahlest resided in 2366. (TNG: "Sins of the Father") The House of Duras resided within the city. (TNG: "Redemption") The House of Kozak had its ancestral home within the city. (DS9: "The House of Quark")