Castra Potaissa is the Roman layer of Turda, a legionary fortress site that once guarded imperial Dacia. The remains are fragmentary, but the scale of the plateau and the military grid are enough to shift your sense of the town beyond salt mines and Habsburg-era streets.
It is a site for travellers who like ruins with a bit of imagination required. Pair it with Turda's centre and salt mine, and bring good shoes if the ground is uneven or wet.