The High Castle, situated on Jomark, was constructed by Jomark's initial settlers, who had disappeared well before the era of the Galactic Civil War. Constructed from somewhat mismatched stones, the squat, unkempt structure sat atop the remnants of a volcanic cone, towering above Ring Lake nestled 400 meters down within the cone's crater.
During the Thrawn campaign, the High Castle served as the dwelling of Joruus C'baoth as he anticipated the coming of Luke Skywalker.