The Early Byzantine and medieval Bulgarian fortress of Markeli (Marcellae in Latin) is located near the eastern Bulgarian town of Karnobat. It was built by the Eastern Roman Empire (Byzantium) at the end of the 5th and the beginning of the 6th century AD. It is unclear whether the name Markeli (Marcellae) is of Ancient Thracian, Roman (Latin), or Celtic origin.
One “Thracian” hypothesis links it to the name of the nearby Mochuritsa River known as Marcil in the past, with the name meaning either a “big river” or a “swampy river”. West of the Markeli Fortress are located the ruins of an ancient bridge built in the 2nd century AD, some 300 years before the fortress. The Markeli Fortress is strategically located to control the southern routes to several major passes through the Eastern Balkan Mountains.
Before the construction of the Early Byzantine fortress, Markeli was the site of an Early Christian martyrium from the end of the 4th and the beginning of the 5th century AD. It existed until the 6th century AD when a three-apse one-nave basilica was constructed on top of it. The basilica was destroyed at the end of the 8th century or the beginning of the 9th century AD.
After the further establishment of the First Bulgarian Empire (632/680 AD – 1018 AD) in the Balkans, in the Lower Danube Valley, and the first expansion of Bulgaria south of the Balkan Mountains in 705 AD, the Markeli (Marcellae) Fortress became the major fortress controlling the road from the then Bulgarian capital Pliska to the Byzantine imperial capital Constantinople. In the late period of the First Bulgarian Empire, Markeli served as a major connection inside the Bulgarian territories. A medieval Bulgarian church was built on top of the ruins of two earlier churches, most likely during the reign of Tsar Simeon I the Great (r. 893-927 AD).
Because of its geopolitical location, the Markeli Fortress is known of its role in the wars between the Bulgarian and Byzantine Empire in the Early and High Middle Ages. In 756 AD, this is where the Bulgarian Khan Vineh (r. 756-760 AD) lost a battle from the forces of Byzantine Emperor Constantine V Copronymus (r. 741-775 AD). However, several decades later, in 792 AD Bulgarian Khan Kardam (r. 777-803 AD) soundly defeated the Byzantine forces of Emperor Constantine VI (r. 780-797 AD) in the Battle of Marcellae, after which the Ancient Bulgar troops chased the Byzantine Emperor all the way to Constantinople.
The Battle of Marcellae is seen as especially important for the early medieval Bulgarian Empire because it put an end to several decades of dynastic strife and relative military weakness of the Bulgarians, and paved the way for the triumph and territorial expansion of the First Bulgarian Empire in the 9th and the 10th century AD.
In 811 AD, the Markeli Fortress was the starting point of the botched military campaign against Bulgaria of Byzantine Emperor Nicephorus I Genikos (r. 802-811 AD) and his son and Co-Emperor Stauracius, which, even though it took and pillaged the Bulgarian capital Pliska, ended in a disastrous defeat in the Battle of the Varbitsa Pass when the forces of the Bulgarian emperor Khan Krum (r. 803-814 AD) annihilated the Byzantine troops and killed both Byzantine Emperors Nicephorus I and Stauracius (who died later of his wounds). Nicephorus I thus became only the second Eastern Roman Emperor to be killed in battle (out of a total of two, or three if the last Byzantine Emperor is counted) in the 1,000-year history of Byzantium, after Emperor Valens (r. 364-378 AD) was killed by the Goths in 378 AD.
After the Varbitsa Pass Battle, Khan Krum turned Markeli into an Ancient Bulgar rampart with huge earthenwork walls. The Markeli Fortress was mentioned in 1089 AD in the works of Anna Komnenos (Comnenus), daughter of Byzantine Emperor Alexios I Komnenos (Alexius I Comnenus) (r. 1081-1118 AD), as a starting point of his campaign against the Pecheneg tribes. The Markeli (Marcellae) Fortress is believed to have been destroyed in 1090 AD by the Cuman tribes in their attack on the Byzantine Empire (which had conquered all of Bulgaria in 1018 AD).
Markeli existed until 1207 AD when it was destroyed by Constantinople’s Latin Emperor Henry of Flanders (r. 1206-1216 AD) in a campaign against the Second Bulgarian Empire (1185-1396 AD). Markeli was mentioned in a map of Bulgaria published in 1791 in Venice by Antonio Zalpa.
The total area of the Bulgarian fortress Markeli (Marcellae) in the Middle Ages, including the territory protected by the Ancient Bulgar rampart walls, is 460 decares (app. 115 acres). The main Early Byzantine fortress wall was 530 meters long. The archaeological discoveries at the Markeli Fortress include five Ancient Bulgar homes with lots of Ancient Bulgar ceramics as well as coins of Byzantine Emperors Justinian I the Great (r. 527-565 AD), Justine II (r. 565-574 AD), John I Tzimiskes (r. 969-976 AD), Nicephorus III Botaniates (r. 1078-1081 AD), Alexios I Komnenos (Alexius I Comnenus) (r. 1081-1118 AD), John II Komnenos (Comnenus) (r. 1118-1143 AD). In 2013, Karnobat Municipality started an EU-funded project worth BGN 3.2 million (app. EUR 1.7 million) for the partial archaeological restoration of the Markeli Fortress completed in 2015.