From A Wiki of Ice and Fire
The Valyrian Freehold was a great territory that spanned much of the continent of Essos, but has since fallen to ruin, approximately one hundred years before Aegon's Landing, when it was brought down by a cataclysmic event known as the Doom of Valyria.
At its prime, the Valyrian Freehold encompassed most of the eastern continent and reached as far as the current Free Cities and the island of Dragonstone off the coast of Westeros. The Valyrian Freehold was technically never an empire  however for ease of reference it tends to be referred to as one.
The Freehold was an advanced civilization and the dominant military and cultural power of the known world. Its capital was the city Valyria. The Freehold was ruled by the Lords Freeholder, powerful noble families. The most powerful of these were the dragonlords.
Valyria was once a minor civilization of peaceful sheep-herding folk dwelling on the Valyrian peninsula until the Valyrians discovered dragons lairing in the Fourteen Fires, a ring of volcanoes on the said peninsula. The Valyrians tamed the dragons with magic and mastered the technique of raising and training the dragons into devastating weapons of war.  They began expanding their influence, establishing the Freehold with Valyria as its capital. There, magic flowered, topless towers rose toward the heavens where dragons soared, stone sphinxes gazed down through eyes of garnet, and smiths forged swords of legendary strength and sharpness; and with their dragons and magic they began expanding their influence.
Rise to Power
Some five thousand years ago, in the early days of Valyria, it was involved in a series of great wars against the Old Ghiscari Empire, which at that time controlled much of the eastern continent. With the help of dragons, Valyria was victorious each time and in the last time they destroyed the Ghiscari Empire, razing its capital Old Ghis to the ground and sowed its fields with salt, sulfur, and skulls. After the conquest of Ghis, Valyria expanded its influence over the surviving Ghiscari colonies of Slaver's Bay and continued to conquer and colonize farther.
War against the Rhoynar
When the Valyrians turned their eyes to the ancient and high civilization of the Rhoynar, Prince Garin the Great led an army of a quarter of a million men against Valyria. However, resistance proved futile and their defeat was disastrous. The remnants fled to Dorne, led by the warrior queen Nymeria. The singers say her 10,000 ships were filled with women and children, suggesting all (or most) of the men of fighting age had died in the conflict with Valyria.
Valyrian Imperialism & Western Expansion
The Valyrian Freehold continued to expand and conquer further west, capturing many slaves from its conquered lands and using them to mine great wealth from the Fourteen Flames, as well as build great cities and roadways that led to Valyria. Cities built by the Valyrian Freehold include Oros, Mantarys, Tyria, and all of the Free Cities except Braavos.
At the height of its power, the Freehold stretched over most of the eastern continent that lay west of the Bone Mountains. Of the fabled great cities, the topless towers are remembered for their great beauty. Some two centuries before the Doom the Valyrian Freehold expanded into the western coastal reaches of Essos. They colonised the island of Dragonstone in the Narrow Sea and established a stronghold there, presumably from which they could trade with the Seven Kingdoms. The island was the westernmost outpost of the Valyrian Freehold.
|“||Odd, that. Dragonstone is no more than a rock. The wealth was farther west, but they had dragons. Surely they knew that it was there. ||”|
Doom of Valyria
The Doom of Valyria was a cataclysmic event that took place approximately one hundred years before Aegon's Landing, following which the city Valyria was utterly destroyed and the Valyrian Freehold crumbled and was no more. The Doom fragmented the land surrounding the city itself into numerous smaller islands, creating the Smoking Sea between them. The area is now described as "demon-haunted", and most people are afraid to go there, as it is said,
|“||The Doom still rules in Valyria. ||”|
Most of Valyria's culture, language, and craft was lost in the Doom, which was followed by the Century of Blood. Valyrian descendants scattered across the world, many across the surviving Valyrian colonies, which gained independence after the Doom and are now known as the Free Cities, and across the cities of Slaver's Bay. The surviving Valyrians intermarried and became mixed with other peoples. Their descendants speak in various local dialects of Valyrian.
Valyria is remembered for its ability to raise and command dragons and using them as weapons of war. This was demonstrated by the Targaryens, the last of the known Valyrian dragonlords, who used that knowledge to conquer and rule the Seven Kingdoms. Valyria is also remembered for forging weapons made of Valyrian steel, a magical alloy used to make weapons of unparalleled quality. The secret of forging such metal was apparently lost with Valyria, making those remaining weapons highly treasured and extremely rare.
The 'Freehold of Valyria' at the zenith of its power was neither a kingdom nor an empire... or at least it had neither a king nor an emperor.  Instead, all free holders, or freeborn landowners, had a say in its governance.
In practice, however, the Freehold was ruled by the Lords Freeholder, powerful noble families. They were forty families of great wealth, high birth, and strong sorcerous ability, those families which controlled and rode dragons in battle, who came to dominate, were known as dragonlords,   The Targaryens were dragonlords, but far from the most powerful.
The people of Valyria were very strong in magic, and they would use their powerful wizards and their dragons in conjunction with their armies to conquer most of the eastern continent. Dragons were controlled by whips, magic horns and sorcery.
The Valyrians spoke the High Valyrian language.
The Valyrians had great skill in shaping stone. It is often said that the old wizards of Valyria did not cut and chisel stone, but worked it with fire and magic as one might work clay, although much of their knowledge is now lost. Valyrians had a powerful magic which could liquefy stone and shape it how they wanted. Valyrian roads, known as dragon roads, still exist as monuments to their work  as well as Dragonstone castle, the Black Wall and the Long Bridge.
The Valyrians used thousands of slaves from across the continent in the blisteringly hot mines underneath the Fourteen Flames to find gold and silver. Slave revolts were common in the mines, but the Valyrians were strong in sorcery and were able to put them down. When there was war, the Valyrians took thousands of slaves, and when there was peace they bred them.
The Valyrians had a number of different gods, among them Balerion, Meraxes and Vhagar.  The singers named Aegon the Conqueror's and his sister's three dragons after those gods, although Aegon converted to the faith of the Seven during the War of Conquest.
The practice of incest was common in old Valyria, as the Valyrians would customarily wed brother to sister.  On Dragonstone the Targaryens continued to practice incestuous marriage and polygamy to keep the dragon bloodline pure.
Books and Scrolls about Valyria
|“||An empire built on blood and fire.||”|
|“||All Valyrian sorcery was rooted in blood or fire. ||”|
It is possible that the titanic clashes between Valyria and the Ghiscari Empire are inspired by the Punic wars between Rome and Carthage over control of the Mediterranean.
References and Notes
- ↑ Citadel, So Spake Martin, June 26 2001
- ↑ 2.0 2.1 A Feast for Crows, Chapter 22, Arya.
- ↑ 3.0 3.1 A Storm of Swords, Chapter 23, Daenerys.
- ↑ 
- ↑ A Dance with Dragons, Chapter 5, Tyrion.
- ↑ A Game of Thrones, Chapter 41, Jon.
- ↑ A Game of Thrones RPG and Resource Book, Guardians of Order
- ↑ A Storm of Swords, Chapter 8, Daenerys.
- ↑ A Feast for Crows, Chapter 28, Cersei.
- ↑ A Dance with Dragons, Chapter 1, Tyrion.
- ↑ 11.0 11.1 A Game of Thrones, Appendix.
- ↑ A Storm of Swords, Chapter 32, Tyrion.
- ↑ So Spake Martin SF, Targaryens, Valyria, Sansa, Martells, and More.June 26, 2001
- ↑ The full story of the Targaryen Conquest in A SONG OF ICE AND FIRE
- ↑ SSM:Targaryens, valyria, June 26, 2001.
- ↑ Chicon 7 Reading (September 02, 2012) So Spake Martin
- ↑ A Game of Thrones, Chapter 23, Daenerys.
- ↑ A Dance with Dragons, Chapter 6, The Merchant's Man (Quentyn I).
- ↑ A Game of Thrones, Chapter 13, Tyrion, p 122.
- ↑ A Clash of Kings, Chapter 12, Daenerys, p 191.
- ↑ A Clash of Kings, Chapter 33, Catelyn.
- ↑ A Dance with Dragons, Chapter 33, Tyrion.
- ↑ A Feast for Crows, Chapter 45, Samwell.