Ulpia Traiana Augusta Dacica Sarmizegetusa was the capital, the first, and largest city of Roman Dacia, named after Sarmizegetusa the former Dacian capital, located some 30 km away. It was founded in 106 as a colonia deducta and elevated to metropolis during the reign of Severus Alexander.The present village of Sarmizegetusa has been built over parts of it.
It acted as the seat of the governor of Roman Dacia until it was moved to Apulum around 158 under Antoninus Pius.
Roman Dacia (/ˈdeɪʃə/ DAY-shə; also known as Dacia Traiana (Latin for 'Trajan’s Dacia'); or Dacia Felix, lit. 'Fertile Dacia') was a province of the Roman Empire from 106 to 271–275 AD. Its territory consisted of what are now the regions of Oltenia, Transylvania and Banat (today all in Romania, except the last region which is split among Romania, Hungary, and Serbia). During Roman rule, it was organized as an imperial province on the borders of the empire. It is estimated that the population of Roman Dacia ranged from 650,000 to 1,200,000. It was conquered by Trajan (98–117) after two campaigns that devastated the Dacian Kingdom of Decebalus. However, the Romans did not occupy its entirety; Crișana, Maramureș, and most of Moldavia remained under the Free Dacians.
After its integration into the empire, Roman Dacia saw frequent administrative reorganization. In 119 under Hadrian, it was divided into two departments: Dacia Superior ("Upper Dacia") and Dacia Inferior ("Lower Dacia"; later named Dacia Malvensis). Between 124 and around 158, Dacia Superior was divided into two provinces, Dacia Apulensis and Dacia Porolissensis. The three provinces would later be unified in 166 and be known as Tres Daciae ("Three Dacias") due to the ongoing Marcomannic Wars. New mines were opened and ore extraction intensified, while agriculture, stock breeding, and commerce flourished in the province. Roman Dacia was of great importance to the military stationed throughout the Balkans and became an urban province, with about ten cities known and all of them originating from old military camps. Eight of these held the highest rank of colonia. Ulpia Traiana Sarmizegetusa was the financial, religious, and legislative center and where the imperial procurator (finance officer) had his seat, while Apulum was Roman Dacia's military center.
Dacia (/ˈdeɪʃə/, DAY-shə; Latin: [ˈd̪aː.ki.a]; Ancient Greek: Δακία) was the land inhabited by the Dacians, its core in Transylvania, stretching to the Danube in the south, the Black Sea in the east, and the Tisza in the west. The Carpathian Mountains were located in the middle of Dacia. It thus roughly corresponds to present-day Romania, as well as parts of Moldova, Bulgaria, Serbia, Hungary, Slovakia, Czech Republic, Poland and Ukraine.
A Dacian kingdom that united the Dacians and the Getae was formed under the rule of Burebista in 82 BC and lasted until the Roman conquest in AD 106. As a result of the wars with the Roman Empire, after the conquest of Dacia, the population was dispersed, and the capital city, Sarmizegetusa Regia, was destroyed by the Romans. However, the Romans built a settlement bearing the same name, Ulpia Traiana Sarmizegetuza, 40 km away, to serve as the capital of the newly established Roman province of Dacia. A group of "Free Dacians" may have remained outside the Roman Empire in the territory of modern-day Northern Romania until the start of the Migration Period.
Sarmizegetusa Regia (also known as Sarmisegetusa, Sarmisegethusa, Sarmisegethuza; Ancient Greek: Ζαρμιζεγεθούσα, romanized: Zarmizegethoúsa) was the capital and the most important military, religious and political centre of the Dacians before the wars with the Roman Empire. Built on top of a 1200 m high mountain, the fortress, consisting of six citadels, was the core of a strategic and defensive system in the Orăștie Mountains (in present-day Romania).
Sarmizegetusa Regia should not be confused with Ulpia Traiana Sarmizegetusa, the Roman capital of Dacia built by Roman Emperor Trajan some 40 km away, which was not the Dacian capital. Sarmizegetusa Ulpia was discovered earlier, was known already in the early 1900s, and was initially mistaken for the Dacian capital, a confusion which led to incorrect conclusions being made regarding the military history and organization of the Dacians.