Ulpia Traiana Sarmizegetusa, Ancient Roman archaeological site in Sarmizegetusa, Romania.

Ulpia Traiana Sarmizegetusa is the walled capital of Roman Dacia, founded in 106 CE on the Hațeg plain at 531 m. Its 32.4-hectare enclosure, 600 by 540 m with 4–5 m walls, held the forum at the crossing of two main streets. Outside stood the stone amphitheatre for about 5,000 spectators, temples and baths; much of the 130-hectare city remains unexcavated.

The settlement was founded after 106 CE as the capital of province Dacia under Emperor Trajan and later gained colonial status under Hadrian. It was abandoned in the 3rd century when Roman administration withdrew from the region.

The city was laid out on a Hippodamian grid, with a tetrapylon at the crossing of the two main streets, each side carrying a fountain dedicated to the nymphs. The forum vetus stood at the centre; a second forum with a Capitolium was built around 153. The Cominii family, who held the highest civic magistracies, built public buildings here.

The site is accessible during daylight and sits in open countryside without shade, so bring sun protection and sturdy shoes. Some areas undergo restoration, meaning barriers occasionally limit access to certain sections.

Fragments of Roman reliefs and inscriptions appear in walls and gardens of nearby houses, where residents have used them as building material for centuries. Local wells still show ancient stone blocks with traces of Roman chisel work.