Locations of the Reach

Highgarden:

The seat of House Tyrell, regional capital of the Reach and the heart of chivalry in the Seven Kingdoms. It lies on the Mander and there the Ocean Road meets the Roseroad, making it an important crossroads.

The Castle
The tiered-walled castle has groves and fountains, shady courtyards, and marble colonnades. It is filled with singers, pipers, fiddlers and harpers. The stables have a fine selection of horseflesh, and there are pleasure boats to sail along the Mander. There are fields of golden roses that stretch as far as the eye can see. Fruits grown nearby include melons, peaches, and fireplums.

History
Highgarden was once the seat of House Gardener, until Aegon the Conqueror defeated King Mern IX Gardener and his host on the Field of Fire, ending their line. When Aegon then marched his host to Highgarden, its steward, Harlen Tyrell, surrendered the castle. For this, Aegon granted him the castle and gave House Tyrell dominion over the Reach.

Oldtown:
One of the largest cities in Westeros and is by far the oldest, built by the First Men before the Andal invasion. The city is located in the south-west of the Reach, at the mouth of the river Honeywine where it opens onto Whispering Sound and the Sunset Sea beyond. It is the western terminus of the Roseroad from Highgarden and King's Landing. House Hightower have their seat at the Hightower in Oldtown. The city also hosts the Citadel, home of the order of Maesters who serve as councillors, doctors, scientists, and postmasters for the Seven Kingdoms.

In the Age of Heroes, what is now the Ravenry of the Citadel was supposedly the stronghold of a pirate lord who sat there robbing ships as they came down the Honeywine. The city's Starry Sept was the seat of the Faith of the Seven until the construction of the Great Sept of Baelor in King's Landing. Oldtown is also one of the most important ports of the Seven Kingdoms. Trading ships from all over Westeros, as well as the Summer Islands, the Free Cities and other places across the narrow sea, constantly crowd into its harbors.

The city itself is stunningly beautiful; many rivers and canals crisscross its cobbled streets, and breathtaking stone mansions are common. The city lacks the squalor of King's Landing, which usurped its position as the pre-eminent city of Westeros. However, the city is a labyrinth of wynds, alleys and streets. West of the Honeywine lie guildhalls, which sit along the shoreline. he largest structure in the city, and also the tallest structure in Westeros, is the Hightower, a massive lighthouse which extends some 800 feet into the sky and is topped by a huge beacon which can be seen for many miles out to sea.

Notably, there is the Thieves' Market and Ragpyckers' Wynd (a street).

Ashford: The seat of House Ashford, and the castle and the town both sit at a fording of the Cockleswent river, just north of the Dornish Marches. The town has whitewashed houses with thatched roofs. Ashford Castle lies next to the town. It is built in the shape of a triangle. It has round towers at each point, thirty feet tall. Between the towers run thick crenellated walls.

The Arbor: An island off the southwestern-most part of Westeros, ruled by House Redwyne. It is considered part of the Reach, and is separated from the mainland by the Redwyne Straits. The port town of Ryamsport is located on the Arbor, as well as the settlements of Vinetown and Starfish Harbor. The Arbor is known for making the best wine in Westeros, especially a terrific red one and a gold wine. Wine from the Arbor is usually sweeter than wine from Dorne. Tourneys held at the Arbor are restricted to knights.

The Shield Islands: Composed of four islands: Greenshield, ruled by House Chester; Greyshield, ruled by House Grimm; Oakenshield, ruled by House Hewett; and Southshield, ruled by House Serry. Also called the Four Shields, the isles are located in the Sunset Sea west of Highgarden and serve as a shield to the Mander river from the Iron Islands. When any sign of longships is spotted, the elders in the watch towers will light the beacon fires, which in turn will cause other watch towers to light their own beacons and spread the warning to various villages and towns and castles further inland so that they will not be caught unaware by any attack.