Ktenia is a ruined Roman

Roman Empire

The Roman Empire was the post-Republican period of the ancient Roman civilization, characterised by an autocratic form of government and large territorial holdings in Europe and around the Mediterranean....

 and medieval

Middle Ages

The Middle Ages is a periodization of European history from the 5th century to the 15th century. The Middle Ages follows the fall of the Western Roman Empire in 476 and precedes the Early Modern Era. It is the middle period of a three-period division of Western history: Classic, Medieval and Modern...

 fortress, situated 2.1 km to the north of the village of Lozarevo

Lozarevo

Lozarevo is a village in the municipality of Sungurlare, in Burgas Province, in southeastern Bulgaria.-References:...

 in Sungurlare Municipality, Burgas Province

Burgas Province

-Municipalities:The Burgas province contains 13 municipalities . The following table shows the names of each municipality in English and Cyrillic, the main town or village , and the population of each as of 2009.-Demography:The Burgas province had a population of 423,608 -Municipalities:The Burgas...

, south-eastern Bulgaria

Bulgaria

Bulgaria , officially the Republic of Bulgaria , is a parliamentary democracy within a unitary constitutional republic in Southeast Europe. The country borders Romania to the north, Serbia and Macedonia to the west, Greece and Turkey to the south, as well as the Black Sea to the east...

. In the Middle Ages, Ktenia often changed hands between Bulgaria

Bulgarian Empire

Bulgarian Empire is a term used to describe two periods in the medieval history of Bulgaria, during which it acted as a key regional power in Europe in general and in Southeastern Europe in particular, rivalling Byzantium...

 and Byzantium

Byzantine Empire

The Byzantine Empire was the Eastern Roman Empire during the periods of Late Antiquity and the Middle Ages, centred on the capital of Constantinople. Known simply as the Roman Empire or Romania to its inhabitants and neighbours, the Empire was the direct continuation of the Ancient Roman State...

.

The ruins of the fortress lie northeast of the town of Sungurlare

Sungurlare

Sungurlare is a town in southeastern Bulgaria, part of Burgas Province. It is the administrative centre of Sungurlare municipality, which lies in the northwestern part of Burgas Province....

, in the Grebenets section of the Eastern Balkan Mountains

Balkan Mountains

The Balkan mountain range is a mountain range in the eastern part of the Balkan Peninsula. The Balkan range runs 560 km from the Vrashka Chuka Peak on the border between Bulgaria and eastern Serbia eastward through central Bulgaria to Cape Emine on the Black Sea...

. In ancient and medieval times, it served as an important defensive position guarding the Karnobat Pass

Karnobat Pass

Karnobat Pass is a 220 m wide and 720 m high pass in Levski Ridge in Tangra Mountains, Livingston Island in the South Shetland Islands, Antarctica. It is bounded by Helmet Peak to the south and Intuition Peak to the north, and is situated 5.46 km east of Lozen Saddle and 5.86 km southeast of...

 through the mountains. Neighbouring castles included Rusokastro

Rusokastro

Rusokastro is a village in the municipality of Kameno, in Burgas Province, in southeastern Bulgaria.-References:...

 to the southeast and Aytos

Aytos

Aytos , sometimes written Aitos and Ajtos, is a town located in eastern Bulgaria some 30 kilometers from the Bulgarian Black Sea Coast and belonging to the administrative boundaries of Burgas Province. It is the administrative centre of the homonymous Aytos Municipality...

 to the east. It is uncertain whether Ktenia is identical with the castle named Goloe, which lay in the same region, or whether these were separate fortifications.

In 705, Ktenia became part of the First Bulgarian Empire

First Bulgarian Empire

The First Bulgarian Empire was a medieval Bulgarian state founded in the north-eastern Balkans in c. 680 by the Bulgars, uniting with seven South Slavic tribes...

 when the Zagore

Zagore

Zagore ; also Zagorie, Zagora, Zagoria) was a vaguely defined medieval region in Bulgaria. Its name is of Slavic origin and means "beyond [i.e. south of] the [Balkan] mountains"...

 area was ceded to Tervel

Tervel of Bulgaria

Khan Tervel also called Tarvel, or Terval, or Terbelis in some Byzantine sources, was the Emperor of the Bulgarians at the beginning of the 8th century. In 705 he received the title Caesar which was a precedent in history. He was probably a Christian like his grandfather Khan Kubrat...

 by the Byzantine Empire. When the Bulgarian Empire

Second Bulgarian Empire

The Second Bulgarian Empire was a medieval Bulgarian state which existed between 1185 and 1396 . A successor of the First Bulgarian Empire, it reached the peak of its power under Kaloyan and Ivan Asen II before gradually being conquered by the Ottomans in the late 14th-early 15th century...

 was reestablished at the end of the 12th century, Ktenia was once again under Bulgarian control until it was conquered by the Byzantines during the Uprising of Ivaylo

Uprising of Ivaylo

The Uprising of Ivaylo was an uprising of the Bulgarian peasantry against the Emperor Constantine Tikh and the Bulgarian nobility. The revolt was fuelled by resentment at the beginning feudalization of the Bulgarian Empire, as well as by the failure to confront the Mongol menace over north-eastern...

 (1277–1280). The fortress was recovered by Bulgaria after a successful war by emperor Theodore Svetoslav

Theodore Svetoslav of Bulgaria

Theodore Svetoslav ruled as emperor of Bulgaria from 1300 to 1322. The date of his birth is unknown. He was a wise and capable ruler who brought stability and relative prosperity to the Bulgarian Empire after two decades of constant Mongol intervention in the internal issues of the Empire...

 (r. 1300–1321) in 1304. However, it was lost during the period of uncertainty after the premature death of his son George II Terter

George II of Bulgaria

George Terter II reigned as emperor of Bulgaria 1321–1322. The date of his birth is unknown, but he was born not long before 1307.George Terter II was the son of Theodore Svetoslav and Euphrosyne, and was named after his paternal grandfather George Terter I. It is possible that he was associated...

 (r. 1321–1322). Ktenia was quickly recaptured by the new emperor Michael Shishman

Michael Shishman of Bulgaria

Michael Asen III ), ruled as emperor of Bulgaria from 1323 to 1330. The exact year of his birth is unknown but it was between 1280 and 1292. He was the founder of the last ruling dynasty of the Second Bulgarian Empire, the Shishman dynasty...

 (r. 1323-1330) in 1324. After another brief Byzantine occupation between 1330 and 1332, it was once again captured by the Bulgarians in the aftermath of the Battle of Rusokastro

Battle of Rusokastro

The Battle of Rusokastro occurred on July 18, 1332 near the village of Rusokastro, Bulgaria between the armies of the Bulgarian and Byzantine Empires. The result was a Bulgarian victory.-Origins of the conflict:...

on 18 July 1332.