Lannisport is a city in the heartlands of The Westerlands and the capital of the region. In canon, it is the region's most populous and prosperous city. It is located next to Casterly Rock, the seat of house Lannister, and administrated by a branch of said noble house.
In the mod, it is a rather unimpressive city economy-wise and frequently overshadowed by its neighbor Kayce. You can recruit Lannister spearmen, as well as the companion Roderick and Martyn Snow, from this town.