Lannisport is the third-largest city in Westeros, after King's Landing and Oldtown. It is located on the west coast of the continent, in the Westerlands. It is located a few miles to the south of Casterly Rock, the stronghold of House Lannister, which looms over the city's northern skyline. Lannisport is home to approximately 300,000 people and is ruled over by a cadet branch of House Lannister.
Lannisport is noted for the skill and training of its City Watch, which has the reputation of being the best-trained feudal levy on the continent.