Goqlath Castle was an ancient structure in Kol'Vat, which was the site of a famous Klingon battle. According to legend, the hero, Krim, slit the throats of the castle guards and led his forces into the fortress and captured it. Some believe it was in the stories of Goqlath Castle that the saying "four thousand throats may be cut in a single night by a running man" originated, though scholars believed the saying predated the conflict, and also that Goqlath Castle was not large enough to accomodate 40,000.
Goqlath Castle is also the name of a Klingon opera which relates the story of this battle. The opera is traditionally attributed to Emperor Sompek, and included the song "The Campaign at Kol'Vat". (TNG novel: Diplomatic Implausibility; KE novel: A Burning House)