The Piatra Roşie fortress has two juxtaposed enclosures placed first on the upper plateau, and the second on the artificial terraces built on the east slope of the cliff. In ancient times, two isolated towers watched the main access road.
The fortification was built during two stages, using two different techniques. The first precinct (on the plateau situated on the top of the cliff) was built after the levelling and the flattening of the terrain.
The plan of the Piatra Roșie fortress is a rectangular one, with corner towers (including a gate tower) and a curtain tower, reminding the architecture of the Hellenistic forts. The entrance to the efortress, through a gate tower was marked by monumental staircases and a vaulted portal, built with profiled stone blocks. During the 1949 research campaign, several decorated iron large nails were found, that were probably fixed into the gate's wood in order to strengthen it as well as to adorn it. The monumental aspect of the fortress entrance is underlined by the limestone slabs paved road leading to the gate tower. To this first main construction stage dates back the rectangular fort as well as the isolated towers that maintained an advanced defensive perimeter.
The defensive structures are built with 3 m thick limestone blocks ramparts. Their structure, inspired from the Hellenistic construction technique, is the following: two parallel walls were built in carved stone (paraments) linked together by wooden beams fixed in special holes carved into the blocks, and the inner space infilled with an emplecton (rubble and earth). The transversal wooden beams, linking together the two paraments, conferred cohesion and durability to the wall. Such type of masonry solution offers a massive and stable rampart, resistant to blows coming from war machines, along with an important construction stone economy. This technique was used to build the ground floors of the isolated towers while the upper floors were built with bricks.
The second precinct, actually an enlargement of a later date, is a rectangular earthen-wooden and also stone rampart, which also includes two of the pre-existing isolated towers. On the inner artificial terraces were constructions still waiting to be studied. The height of the Antiquity walls can be estimated to 5-6 m, while the towers were probably taller. The appearance of the upper part of the ramparts is unknown. C. Daicoviciu made the assumption of some wooden platforms, but the crenellation is not excluded either, since its utility during battle.
The existing data seem to indicate the use of the fortress at least since the second half of the Ist century BC and probably to the Roman conquest. Traditionally, according to cultural and historical criteria, the first enclosure was dated for the first part of this interval while the extension of the fortification (the second enclosure) was situated in the period immediately previous to the Dacian-Roman wars. The end of the fortress, for the same reasons, was connected to the Roman conquest.
The analysis of the findings shows a flourishing period for the fortress during the Ist century BC and the following century.
Certain findings are indicating also an early Middle Age occupation of the site.
In the northern sector of the upper plateau, outside the walls, a temple was in use for a certain period of time (of the wooden column alignment type, erected on limestone bases) from which several plinths (stone disks) are still to be seen today. It is probable that, at a certain moment, two buildings with multiple rooms (of a still unknown destination) took the place of that temple on the same spot.
Civilian constructions/ facilities
The great apse-shaped building with porch, on the upper plateau, occupies a large part of the usable surface of the Fortress I, demonstrating its central position and its importance. Built of wooden beams, placed on stone block bases, it probably was the residence of a chieftain as the findings discovered in it seem to prove
The road paved with limestone slabs crosses the second precinct, climbs towards the entrance tot he first enclosure and a small branch of it goes towards the apse construction on terrace I.
The apse construction on the first terrace was built of beams placed on stone bases. The discovery in the semicircular chamber of the wrought iron disk ("the Piatra Roșie shield”), richly adorned, could suggest the building's religious destination. The specifics of the antique ritual activities often shows that the line between the two sides of existence - the sacred and the profane - was not always clear.