Oescus, Palatiolon[1] or Palatiolum[2] (Bulgarian: Улпия Ескус, pronounced [oɫˈpiɐ ˈɛskos]) was an important ancient city on the Danube river in Roman Moesia.

90–168 AD) described Ulpia Oescus as a city of the Triballi, an independent ancient tribe which inhabited today’s northwestern Bulgaria.

[5] Under Roman rule, Oescus began as an important military base and legionary fortress as part of the Danubian Limes.

An aqueduct was built to deliver fresh water from springs 20 km away, and a stone wall was constructed to protect the site from invaders and from the Danube floods.

Remains of the legionary fortress's defensive wall are still visible and areas to the east-northeast (Pyasutsite and Prez Livada) show signs of the presence of a necropolis from this period, containing epigraphic monuments of veterans.

[4] Other artifacts from the site, such as a statue of the goddess Fortuna, are on view at the National Archaeological Museum in Sofia.

[4][7] Archaeological surveys of the eastern extension of Oescus II indicate houses from the Principate period, some of which were quite massive and were decorated with mosaics that could be dated to the time of Septimius Severus.

[4] There are a main gate, administrative buildings, a civil basilica, three public baths (thermae), wells, a perfectly preserved road, pagan temples, a necropolis, defensive walls, workshops, and a forum.

In 2020 the Aula regia, or great hall, was found to have been exquisitely and elaborately decorated with 14 types of rare multicloured marble.