Valyria

At its height Valyria occupied a peninsula off southern Essos, washed by the Summer Sea, linked by roads to Tyria and three other cities of the Freehold. Travelers on those roads felt they were heading toward the point where everything else converged.

The city grew upward: towers so tall they vanished from sight, threaded by lava from the Fourteen Fires that the pyromancers put to use. Sphinxes lined its streets. Power was split between two rival dragonlord houses, who occasionally handed rule to an archon chosen from among them.

Beneath that wealth lay mines of gold and silver, worked by slaves captured in the wars against Ghiscar and the Rhoynar. That system held the empire together for generations — until it didn't.

Valyria was the ancestral home of House Targaryen, and of the Velaryons and Celtigars too. When Daenys, daughter of Lord Aenar Targaryen, dreamed that the city would one day be destroyed, her father chose not to wait and see if she was right.

Aenar got his family to safety, along with the five dragons the house still had and whichever allied houses chose to follow, crossing the sea to Dragonstone, the island that became their new home.

Around the year 102 before the Conquest, something devastated Valyria in a single day. Accounts speak of fire pouring from the Fourteen Fires, of the ground splitting open, of a sky turned to ash. Every soul in the city died, and the entire Freehold fell with it.

Of the empire that had ruled half the known world, no government, no army, no noble house remained to claim what was left. Only a handful of dragonlords, already far from the city when it happened, lived to tell of it.

Shortly after the catastrophe, Aurion — one of the few dragonlords left alive after the ruin — declared himself Emperor of Valyria and marched his army out to reclaim whatever still stood. Neither he nor his men were ever heard from again.

Later, the Volantene party of the Tigers sent an entire fleet to occupy the ruins; it vanished in the Smoking Sea without a trace. Tommen II Lannister, King of the Rock, tried too, drawn by riches said to still lie buried there, and met the same end.

Valyria is still said to hold Valyrian steel swords and other objects of power left over from before the ruin. No one who has gone to check has come back to confirm it.

During the reign of Jaehaerys I Targaryen, his niece Aerea — heir to the throne before his own children were born — vanished along with Balerion, the oldest and largest dragon still living. Almost two years passed with no word of either of them.

When Aerea reappeared over King's Landing, riding a wounded Balerion, something was eating away at her from inside; she died soon after. Septon Barth came to believe the dragon had carried her to Valyria, the place where both had been born, and that the Doom had touched them there.

For years the story went that in 115 AC, Daemon Targaryen and Laena Velaryon flew Caraxes and Vhagar all the way to the ruins of Valyria itself, defying the Doom to see with their own eyes what was left of the old dragonlords' empire. What they actually did was simpler: they flew to the Free Cities.

Gerion Lannister really did try. He set out for Valyria in 291 AC in search of Brightroar, the Valyrian steel blade his house had lost generations before. He never returned; he is presumed to have died at sea.

Euron Greyjoy claimed to have done what no one else managed: reaching Valyria and coming back alive. He said that among those ruins he found the Dragonbinder horn, a dragon's egg, and other treasures no one else could claim.

No one could prove the story true or false, but it gave him more standing at the Kingsmoot than any other claimant, and he ended up crowned King of the Iron Islands on the strength of it.