Ratiaria

43°49′01″N 22°54′28″E / 43.81694°N 22.90778°E / 43.81694; 22.90778

Ratiaria (or: Ratsaria, Raetiaria, Retiaria, Reciaria, Razaria; Bulgarian: Рациария; Greek: Ραζαρία μητρόπολις;) was an ancient Roman city along the river Danube. A Roman colony was established there, called Colonia Ulpia Traiana Ratiaria.

It is located 2 km west of the present village of Archar in Vidin Province, northwestern Bulgaria and 3 km east of the present Balta Neagră Natural Reserve in southern Romania. The closest modern cities are Vidin (27 km to the north west), Lom (28 km to the east) in Bulgaria and Calafat (41 km to the north) in Romania.

An archaeological museum for the site has recently been established in Dimovo.