The Valyrian Peninsula is a large headland extending south from Essos into the Summer Sea. It is located south-east of the Free Cities and west of Slaver's Bay. It was the former location of Valyria, the capital city of the Valyrian Freehold. The southern part of the peninsula was destroyed in the volcanic cataclysm known as the Doom of Valyria some four hundred years before the War of the Five Kings.
The Valyrian Peninsula was originally about 900 miles long from north to south and was about 600 miles across from east to west, at its widest point. The Doom shattered the southern third or so of the peninsula, reducing it to three large and numerous smaller islands surrounding by smouldering waters (an area known as the Smoking Sea). The main breach came along the volcanic chain known as the Fourteen Fires, at least some of which survived the Doom to continue belching smoke and lava into the sky.
Most of the Valyrian Peninsula is uninhabited, lying as it does in the shadow of the Fourteen Fires and the volcanic debris they continue to emit. The Lands of the Long Summer, formerly the Valyrian hinterland, are located on the peninsula and are no longer settled. The western half of the peninsula is dominated by the Sea of Sighs, at the northern tip of which lies the city of Mantarys. The largest settled city on the peninsula, Mantarys is considered a nightmarish city of demons and is shunned by travellers and merchants, who prefer to take the much longer (but much safer) sea trip right around Valyria instead.
Valyrian roads criss-cross the peninsula, having survived even the Doom, but are no longer regularly used. The road stretching across the neck of the peninsula is known as the Demon Road between Volantis and Tolos (the stretch centered on Mantarys) and is also shunned, for the same reasons that Mantary is avoided.