The Arbor is a large island off the southwestern coast of Westeros, separated from the mainland by the Redwyne Straits. It is part of the Reach and its rulers, House Redwyne, hold fealty to House Tyrell of Highgarden. House Redwyne controls a large fleet from the Arbor. The Arbor is famous across much of the known world for its high-quality wines.
King Stannis Baratheon composes a letter revealing the truth of Cersei Lannister's incestuous relationship with her brother Jaime, and that Jaime is the real father of Joffrey Baratheon, and orders that copies of the letter be sent to every corner of Westeros, "from the Arbor to the Wall".
In the books
In A Song of Ice and Fire, the Arbor is the biggest shipyard in southern Westeros. Its fleet is one of the largest in the realm, behind only the King's Fleet and the Iron Fleet of the Iron Islands. The Arbor has a warm and pleasant climate, due to its position surrounded by water off Westeros' southern coast. This climate is ideal for viticulture, and the Arbor is home to vast vineyards. Locations on the Arbor include Starfish Harbor and Vintown.
Old Oak · Red Lake · Goldengrove · Bitterbridge · Tumbleton · Grassy Vale · Cider Hall · Ashford · Horn Hill · Brightwater Keep · Bandallon · Honeyholt · Oldtown (The Citadel · The Hightower) · Uplands · Blackcrown · Three Towers · Sun House · The Arbor
Shield Islands · The Arbor