The castle ruin from Deva was one of the most important royal castles of the Mureş River's valley, and it is the result of several construction phases. It is presently composed of four precincts, among which the Upper Castle of an irregular oval shape, orientated to east-west, is the most significant. During the revolution of 1848–49 it's gunpowder storage exploded, and it has been in ruin ever since. The conservation of this important tourist attraction is under way.

The fortress of Orăştie is actually composed of the Calvinist and Lutheran Churches, which are surrounded by a fortification wall dating from the 15th century, strengthened by three bastions and three corner-towers. Archaeological researches have revealed the existence of an earth castle from the 10-11th centuries and have unearthed a stone rotunda, which, due to its strategic location, was probably fortified itself. The earth castle was demolished in the 13th century, however, its stone tower was included in the subsequent fortification, its masonry being still visible.

Sarmizegetusa Regia was the capital – the political and military centre – of the ancient Dacian state. It reached the peak of it's evolution during the leadership of Decebal, during which the fortress, built of massive stone blocks (murus dacicus), extended upon four terraces, including a sacred area, where the famous circular shrines are to be seen even today. The fortress was demolished on the order of Emperor TRAJAN. In 1990 it was declared a UNESCO World Heritage Site along with other Dacian fortresses.

Hunedoara Castle is one of the most intactly preserved historic buildings from the second part of the 15th century and the most faithful reflection of King Sigismund's Buda Palace (today Budapest). The irregular stone fortress that constituted the castle's core was built in the 13th century, then modernised and “made inhabitable” by governor John HUNYADI, respectively his son, King Matthias I. It's present aspect is the result of the arguable conservation works from the 19-20th centuries.

The first castle of the Oradea, founded according to tradition by King St. Ladislaus I, was an earth castle, which was gradually strengthened by stone walls, after which it was replaced in the Renaissance period (1586–1629) by a pentagonal fortress, protected at its corners by Italian bastions. In the interior of this borderline castle another pentagonal building, the princely palace was built in late Renaissance style. During the 18th century a garrison was stationed in the fortress, due to which a number of annexes were constructed in the fortress.