Oescus

Colonia Ulpia Oescensium
Section of legionary fortress wall, Oescus
Known also as	Oescus
Founded during the reign of	Trajan
Founded	102
Abandoned	586
Province	Mesia superiore
Limes	Danube
— Legions —
Legio V Macedonica da Augusto a Traiano
Town	Gigen
County	Gulyantsi Municipality
State	Pleven District
Country	Bulgaria

Coordinates: 43°42′N 24°29′E / 43.700°N 24.483°E / 43.700; 24.483

Oescus, or Palatiolon Palatiolum, (Bulgarian: Улпия Ескус, pronounced [ul.ˈpi.a ˈɛs.kus]) was an ancient town along the Danube river, in Moesia, northwest of the modern Bulgarian city of Pleven, near the village of Gigen. It is a Daco-Moesian toponym. Ptolemy calls it a Triballian town, but it later became Roman. For a short time, it was linked by a bridge with the ancient city of Sucidava (modern-day Corabia - Romania). The city seems to have at one point reached a size of 280,000 m² and a population of 100,000.

The Greco-Egyptian geographer Claudius Ptolemy (ca. 90-168 AD) described Ulpia Oescus as a city of the Triballi, an independent Ancient Thracian tribe which inhabited today’s Northwest Bulgaria.

The name of the Roman town comes from the river Oescus (today Iskar). It probably meant "water" in the local Thracian dialect.