Tulcea County in the context of "Battle of Ongal"

Dobruja or Dobrudja (US: /ˈdoʊbrʊdʒə/; Bulgarian: Добруджа, romanized: Dobrudzha or Dobrudža; Romanian: Dobrogea, pronounced [ˈdobrodʒe̯a] or [doˈbrodʒe̯a]; Turkish: Dobruca; Ukrainian and Russian: Добруджа, romanized: Dobrudzha) is a geographical and historical region in Southeastern Europe that has been divided since the 19th century between the territories of Bulgaria and Romania. It is situated between the lower Danube River and the Black Sea, and includes the Danube Delta, the Romanian coast, and the northernmost part of the Bulgarian coast. The territory of Dobruja is made up of Northern Dobruja, which is a part of Romania, and Southern Dobruja, which is a part of Bulgaria.

The territory of the Romanian region Dobrogea is organised as the counties of Constanța and Tulcea, with a combined area of 15,588 km (6,019 sq mi) and, as of 2021, a population of slightly less than 850,000. Its main cities are Constanța, Tulcea, Medgidia, and Mangalia. Dobrogea is represented by dolphins in the coat of arms of Romania.

The Danube Delta (Romanian: Delta Dunării, pronounced [ˈdelta ˈdunərij] ; Ukrainian: Дельта Дунаю, romanized: Del'ta Dunaju, pronounced [delʲˈtɑ dʊnɐˈju]) is the second largest river delta in Europe, after the Volga Delta, and is the best preserved on the continent. Occurring where the Danube River empties into the Black Sea, most of the Danube Delta lies in Romania (Tulcea County), with a small part located in Ukraine (Odesa Oblast). Its approximate surface area is 4,152 square kilometres (1,603 square miles), of which 3,446 km (1,331 sq mi) is in Romania. With the lagoons of Razim–Sinoe (1,015 km or 392 sq mi with 865 km or 334 sq mi water surface), located south of the main delta, the total area of the Danube Delta is 5,165 km (1,994 sq mi). The Razim–Sinoe lagoon complex is geologically and ecologically related to the delta proper; the combined territory is listed as a World Heritage Site.

The Măcin Mountains (Romanian: Munții Măcin) is a mountain range in Tulcea County, Romania. Part of the Northern Dobruja Massif, they are located between Danube River to the north and west, Taița River and Culmea Niculițelului to the east and Casimcea Plateau to the south. Seen from the Danube, they seem only low hills. However, they are a mountainous region.

The Măcin Mountains are one of the oldest in Romania, being formed in the second part of the Paleozoic, in the Carboniferous and Permian, during the Hercynian orogeny. The predominant rock is granite. Erosion (caused by the difference of temperature) has created steep slopes, with the aspect of ruins.

In ancient geography, Peuce (Ancient Greek: πεύκη, romanized: peúkē, lit. 'pine tree') is a former island in the Danube Delta, in Scythia Minor (present-day Tulcea County, Romania). It was about the size of the island of Rhodes. The inhabitants of the island were called Peucini (Ancient Greek: Πευκῖνοι).

It was to this island that in the 330s BC the West Thracian Triballian king Syrmus took refuge when pursued by Alexander the Great. Alexander brought ships up the Danube to use in an assault on the island. The attempts failed due to the swift current of the river, steep banks, and fierce defense. Eventually the Macedonians abandoned their attacks on Peuce and instead crossed into the territory of the Getae.

Tulcea (Romanian pronunciation: [ˈtult͡ʃe̯a]; also known by alternative names) is a city in Northern Dobruja, Romania. It is the administrative center of Tulcea County, and had a population of 65,624 as of 2021. One village, Tudor Vladimirescu, is administered by the city. It is one of six Romanian county seats lying on the river Danube.

The Taița is a river in Tulcea County, Romania. North of the town Babadag it discharges into Lake Babadag, which is connected with Lake Razim, a former lagoon of the Black Sea. Its length is 57 km (35 mi) and its basin size is 591 km (228 sq mi).

Chilia Veche (Romanian pronunciation: /kiˈlija ˈveˈke/; meaning Old Chilia) is a commune in Tulcea County, Northern Dobruja, Romania, in the Danube Delta. It gave its name to the Chilia branch of the Danube, which separates it from Ukraine. It is composed of four villages: Câșlița, Chilia Veche, Ostrovu Tătaru and Tatanir.

Founded by the Greek Byzantines, it was given its name after the word for "granaries" - κελλίa, kellia, recorded earliest in 1241 in the works of Persian chronicler Rashid al-Din. Some scholars consider the mediaeval Genoese trade centre known as Lycostomo (Λυκόστομο) was also located here. A town on the other side of the Danube, now in Ukraine, known as Nova Kiliia (Romanian: Chilia Nouă) or "New Chilia", was built by Stephen the Great of Moldavia in order to counteract the Ottoman Empire (that had taken control of the former town in the 15th century).