Iron Age (11th–1st Century BCE)

During the first millennium BCE, Thrace was one of Europe's most densely populated regions. According to Herodotus, the "father of history": "The Thracian people, after the Indian, is the greatest of all peoples. If it were ruled by one master and united, it would be, in my opinion, invincible and far stronger than all other peoples..." (Histories. V. 3).

As in the Bronze Age, Early Iron Age Thracians (11th–6th century BCE) lived in both the plains and mountains of present-day Bulgaria. Their settlements were small—no more than a dozen houses—but clustered close together. They built wattle-and-daub dwellings with stone foundations several rows high (or none at all), walls of poles woven with branches and plastered with clay, and light roofs made of branches. Most homes had a single room with a small hearth.

In the first half of the 5th century BCE, the kingdom of the Odrysians—one of the largest Thracian tribes—emerged along the Tundzha and Maritsa rivers. Thracian cities appeared as trading centers and political hubs for Thracian aristocrats, featuring impressive architecture and powerful fortifications. Archaeological excavations have uncovered numerous luxury items, revealing the wealth of their inhabitants. Notable cities included Philippopolis (present-day Plovdiv), Cabyle (near Yambol), Pistiros (near Septemvri), and sites near the villages of Krastevich (near Hisarya) and Koprivlen (near Gotse Delchev). During the Late Iron Age, Thracian kings and aristocrats lived in fortified, compact residences called thyrseis.

In the late 4th to early 3rd century BCE, political capitals emerged in Thrace—cities from which local rulers governed their territories. One such capital was Seuthopolis, the seat of Seuthes III, which today lies at the bottom of the Koprinka reservoir near Kazanlak. It had powerful fortifications, a central square, streets, and residential, administrative, and religious buildings. In the northeastern corner stood a fortified residence housing the royal palace and a sanctuary to the Great Samothracian Gods. Another important urban center in northeastern Thrace was located at "Sboryanovo" near present-day Isperih. Archaeologists identify it as Helis, the ancient capital of the Getae ruler Dromichaetes. An earthquake destroyed this city in the mid-3rd century BCE.

The Thracians' main occupations were agriculture and animal husbandry. Most Thracian peasants lived in small villages surrounded by fertile land and built near water sources. They relocated frequently, so their dwellings had light constructions that are rarely uncovered in archaeological excavations. The Thracians lived in above-ground or semi-subterranean huts with thatched roofs and walls made from poles woven with branches. Floors were plastered with clay, and rooms contained hearths, ceramic vessels, and tools. The Greek author Xenophon recounts that each family had its own yard, "fenced in for the sheep" with a wattle fence that could easily be jumped over.

Roman Period (1st–4th Century CE)

The incorporation of Thracian lands into the Roman Empire transformed this system of settlement. Some cities gradually developed upon earlier settlements, adopting typical imperial organization and buildings. Others were built entirely during the Roman period. Examples of the latter include Nicopolis ad Istrum, near present-day Nikyup in the Veliko Tarnovo region; Novae near present-day Svishtov; Transmarisca, present-day Tutrakan; and Nicopolis ad Nestum, present-day Garmen in the Blagoevgrad region. These cities featured straight, paved streets, spacious squares (forums), water supply systems, and sewage. Water for public fountains and baths was often brought from dozens of kilometers away using special structures called aqueducts. New public buildings included basilicas, theaters, temples, baths, libraries, amphitheaters, and stadiums, many decorated with beautiful mosaics and marble statues. Wealthy citizens lived in large houses, closed from the outside but open to an inner courtyard, often with a colonnade and garden. They could also afford suburban estates—villas equipped with every convenience. A special type of city was the newly built colony. This was a pre-planned settlement modeled on Rome, whose inhabitants enjoyed various privileges. In Bulgaria, these include Oescus, near present-day Gigen in the Pleven region; Ratiaria, near present-day Archar in the Vidin region; and Deultum, near present-day Debelt in the Burgas region. Even today, well-preserved Roman structures can be seen throughout Bulgaria, including the ancient theater and stadium in Plovdiv; the baths in Varna, Hisarya, Debelt, and Kyustendil; the amphitheater in Sofia; and the Roman squares and streets in Stara Zagora.

Well-maintained roads connected all parts of the Roman Empire. Along with aqueducts and sewage systems, they are one of the greatest contributions of Roman builders and architects. Roman roads were built with exceptional durability; nearly 2,000 years later, preserved sections still exist throughout Bulgaria and Europe.

Several major imperial roads passed through the modern territory of Bulgaria. The most important was the Via Diagonalis, also called the Military Road, which connected the eastern and western parts of the empire. It passed through present-day Plovdiv and Sofia and exceeded 900 km in total length. The Danube Road was built during Emperor Trajan's reign along the river's right bank. Many Roman military camps and watchtowers were constructed along it to guard the empire's border (limes) at the Danube River. The Via Pontica was a coastal road that connected Constantinople with cities along the Black Sea coast.

The Romans built road stations at regular intervals to serve messengers, postal carriers, and merchants. Travelers could eat, rest, and exchange tired horses. Many of these stations eventually grew into settlements and marketplaces, with some becoming fortifications.