Narrow Sea

The Narrow Sea is the sea that lies to the east of Westeros. It separates Westeros from the larger continent of Essos to the east. The sea is relatively narrow and easy to cross, although still large enough to make large-scale invasions and military incursions between the Seven Kingdoms and the Free Cities difficult.

In the books
In the Song of Ice and Fire novels, the Narrow Sea is a Mediterranean-sized body of water separating Westeros from Essos. The Narrow Sea runs from roughly just east of the Vale to just north-east of Dorne. In the north it opens out into the circumpolar ocean known as the Shivering Sea (whichs separates Essos from the northern icecap), whilst in the south it is divided from the larger Summer Sea by the island-chain known as the Stepstones. The Westerosi cities of Gulltown and King's Landing lie on its western shores, and the Free Cities of Braavos, Pentos, Tyrosh and Myr lie on its eastern shores. The Free Cities of Lys and Lorath lie on islands in the Narrow Sea, close to the Essos coast. Braavos has the largest and most powerful navy on the Narrow Sea.