From A Wiki of Ice and Fire
Valyrian roads are broad stone highways built when the Valyrian Freehold dominated Essos. They are straight and usually ran from one economic center to another, allowing swift transport of goods. They are also known as dragon roads.
Valyrian roads ran across much of the Valyrian peninsula, connecting the cities of Valyria, Tyria, and Oros with outlying settlements. The peninsula and its cities were shattered in the Doom of Valyria, however. A road continues north from the ruins of Oros through the Lands of the Long Summer to Mantarys. The demon road runs from Meereen westward past Mantarys to Volantis on the Rhoyne; a branch of the demon road also runs south to Tolos near the Black Cliffs. A road continues north from Volantis to the ruins of Sar Mell.
In northern Essos, a Valyrian road runs east from Pentos on the narrow sea to the ruins of Ghoyan Drohe in the Velvet Hills. From Ghoyan Drohe it runs northeast to Norvos and then southeast to Qohor. From the latter city a road connects to the ruins of Ar Noy to the southwest. A road continues east from Qohor to the ruins of Vaes Khadokh (Essaria) and Vaes Khewo (Sarnath). Another road runs north from Vaes Khadokh to Saath on the Shivering Sea.
A Game of Thrones
A Dance with Dragons
At the start of his journey from Pentos to Volantis, Tyrion Lannister takes the opportunity to have a closer look at the Valyrian road that he and Illyrio Mopatis are traveling on. It runs as straight as a spear to the horizon. It is a ribbon of fused stone raised half a foot above the ground to allow rainfall and snowmelt to run off its shoulders. Tyrion muses that unlike the muddy tracks that pass for roads in the Seven Kingdoms, the Valyrian roads are wide enough for three wagons to pass abreast, and neither time nor traffic mar them. They still endure, unchanging, four centuries after Valyria itself had met its Doom.