Castle Black is the main fortress for the Night's Watch. The castle is situated along the Wall between Queensgate to the west and Oakenshield to the east, near the center of the Wall, at the northern end of the Kingsroad. The village of Mole's Town is located half a league to the south along the Kingsroad.
Despite there being nineteen strongholds along the Wall, Castle Black is one of only three still manned by the Night's Watch, the others being the Shadow Tower and Eastwatch-by-the-Sea. The castle once held over five thousand men, but it now currently holds about six hundred brothers.
Winterfell is the ancestral castle and seat of power of House Stark and is considered to be the capital of the North. It is located in the center of the northern province of the Seven Kingdoms, on the Kingsroad that runs from King's Landing to the Wall.
Winterfell was supposedly built by Brandon the Builder over eight thousand years ago, with the help of giants. For most of recorded history Winterfell was the seat of House Stark, the Kings in the North and later as Wardens of the North, after King Torrhen Stark bent the knee to Aegon the Conqueror and his dragons. As the regional capital of the North, harvest festivities have been hosted in Winterfell for centuries.
The Twins, sometimes known as the Crossing, is the name given to the fortified river crossing of House Frey within the northern Riverlands. It is the seat of House Frey
The Twins consists of two identical castles standing on a margin of the Green Fork of the Trident. A stone bridge arches between them. This bridge is wide enough for two wagons to cross abreast, and is guarded by a tower in the middle known as the Water Tower. It is the only crossing point over the Green Fork for hundreds of miles in either direction, from the North to the western Riverlands. It lies directly athwart the main route from Winterfell to Riverrun.
The Eyrie is the ancient seat of House Arryn, one of the oldest lines of Andal nobility. It is situated in the Mountains of the Moon astride the peak known as the Giant's Lance, several thousand feet above the valley floor below. It's considered impregnable to attack. During winter years, the Arryns seek refuge against the cold at the base of the mountain in the Gates of the Moon.
King's Landing is the capital of the Seven Kingdoms, located in the Crownlands on the east coast of Westeros, overlooking Blackwater Bay. It is the site of the Iron Throne and the Red Keep, the seat of the king. The main city is surrounded by a wall, manned by the City Watch of King's Landing, also known as the gold cloaks. Poorer smallfolk build shanty settlements outside the city. King's Landing is extremely populous, but rather unsightly and dirty compared to other cities. The stench of the city's waste can be smelled far beyond its walls. It is the principal harbor of the Seven Kingdoms, rivaled only by Oldtown.
Pentos is one of the Free Cities. It is a port located on the western coast of Essos.
Pentos was one of the Valyrian colonies in western Essos. When the Doom destroyed the empire four centuries ago, Pentos became an independent city state. When the Tattered Prince was 23 the magisters of Pentos chose him to be their new prince almost right after they have beheaded the previous one. Instead of accepting their offer he fled to the Disputed Lands, later forming the Second Sons. Thus far he has never returned to Pentos.
Qarth is an ancient port city located on the south coast of the Essos continent. Situated in a central location, Qarth is a gateway of commerce and culture between the east and west, and the north and south. Brimming with wealth, the city's architecture makes a grand display. It is home to warlocks and merchant princes, and nominally ruled by the Pureborn. However, the powerful guilds Thirteen, Tourmaline Brotherhood and the Ancient Guild of Spicers all attempt to play a role in the governance of the city. It has been referred to as the Queen of Cities. On entering Qarth, Daenerys thinks to herself that the magnificence of the city cannot be denied.
Pyke is a castle located on the island of the same name, which is one of the seven Iron Islands. It is the seat of House Greyjoy, the rulers of the Iron Islands. 'Pyke' is also the name given to bastards born on the Iron Islands.
During the Greyjoy Rebellion, the Siege of Pyke was the final battle. King Robert, along with Lord Eddard Stark mustered thousands of men, invading the islands thorough Lordsport and won after they brought down the southern part of the outer wall of Pyke, using siege engines.
Riverrun is the ancestral castle of House Tully, held by them for over a thousand years. It is situated in the Riverlands, at the point where the Tumblestone and Red Fork rivers meet.
During the War of the Five Kings, Riverrun is besieged by a Lannister host commanded by Jaime Lannister. It is relieved in the Battle of the Camps by a Stark force commanded by Robb Stark. In the Great Hall of Riverrun Robb is elevated to King in the North by his Northern bannerman as well as the river lords, who have never been part of the old Northern kingdom.
Casterly Rock, nicknamed the Rock, is a fortress and the seat of House Lannister. The capital of the Westerlands, it overlooks the harbor of Lannisport and the Sunset Sea.
The Rock has never fallen. The Lannisters trace their rule over it back to Lann the Clever, who tricked the Casterlys out of their castle and claimed it for his own. After Harrenhal, the Rock is most likely the second-largest castle in the realm.