Korranberg is the oldest city in Zilargo, nestled against the base of the Seawall Mountains. It's not the capital, but is arguably still the most important settlement in Zilargo because of the Library of Korranberg, which beyond just being a library and a university, is perhaps the greatest collection of knowledge on Eberron. It is also the home and distribution center of the Korranberg Chronicle, which is among the most respected newspapers in Khorvaire, and one of the only ones available anywhere on the continent.
The Triumvirate of Zilargo, which rules the nation, was originally founded in Korranberg. Though the Triumvirate is now based in Trolanport, one of it's representatives is still chosen from Korranberg.
All of the dragonmarked houses have a presence in Korranberg, but the city is the headquarters and ancestral home of House Sivis. House Cannith is represented in Zilargo by Cannith South.