Carsium was a fort in the Roman province of Moesia in the 1st century AD whose remains are still visible. It was part of the defensive frontier system of the Limes Moesiae along the Danube.
It defended a nearby Danube crossing ford, one of the most important on this segment of the limes and the road that crossed into Dacia.
A Roman settlement grew up on the site of the current town of Hârșova around the Roman fort. It was initially in Moesia and later in Scythia Minor province.
Wikipedia https://en.wikipedia.org/wiki/Carsium_(castra)
Address 1 Strada Cetății, Hârșova 905400, Romania
Coordinates 44°40'54.497" N 27°57'7.623" E