It was an independent kingdom until long after Aegon the Conqueror's day, until it was brought into the realm by political alliance and marriage into House Targaryen just over a century ago. House Martell rules over Dorne from the castle of Sunspear.
The Dornish are nationalistic and independently-minded, far moreso than the other peoples of Westeros. The blood of the Rhoynar runs strong in them. The Dornish are passionate, quick to anger and to laugh, but can be sly and cunning when needed. The Dornish make strong allies and formidable enemies.
Bastards born in Dorne take the surname 'Sand'.
Dorne is in the southern-most part of Westeros. It is on the peninsula because it is bordered by the Sea of Dorne to the north. The capital of Dorne is Sunspear, where the ruling family of the region (the House Martell) resides.
The other major cities in Dorne are Starfall, Yronwood, and Planky Town.
Dorne produces many products that are not easily found in the other kingdoms. They produce citrus fruits, wine, lemons, olives, pomegranates, and more.
Another notable fact about Dorne is that the town is famous for its horses, called the sand steed, a slim but fast horse that can run for two days without tiring.