At-Tabqa , Minaret of the Mosque at Jaʿbar Castle.

At-Tabqa , Minaret of the Mosque at Jaʿbar Castle.

A general view of the remains of Shayzar Castle

A general view of the remains of Shayzar Castle

At-Tabqa, Jaʿbar Castle , one of the Castle's towers.

At-Tabqa, Jaʿbar Castle , one of the Castle’s towers.

At-Tabqa , Jaʿbar Castle, Bastion with loopholes.

At-Tabqa , Jaʿbar Castle, Bastion with loopholes.

At-Tabqa, Jaʿbar Castle, Entrance of a bastion with loopholes

At-Tabqa, Jaʿbar Castle, Entrance of a bastion with loopholes

at-Tabqa, Jaʿbar Castle, Towers of western walls

at-Tabqa, Jaʿbar Castle, Towers of western walls

at-Tabqa, Jaʿbar Castle, polygonal tower.

at-Tabqa, Jaʿbar Castle, polygonal tower.

Jaʿbar castle, southern side of the castle

Jaʿbar castle, southern side of the castle

at-Tabqa, Jaʿbar Castle, Towers of western walls

at-Tabqa, Jaʿbar Castle, Towers of western walls

Dura Europos (Qalʿat as-Salihiyya), Roman amphitheater

Dura Europos (Qalʿat as-Salihiyya), Roman amphitheater

Palmyra, Colonnaded axis and Qalʿat Ibn Mʿan in the back

Palmyra, Colonnaded axis and Qalʿat Ibn Mʿan in the back

Euphrates valley south of Qalʿat Najm as it looked before the flooding of lake Tishrin

Euphrates valley south of Qalʿat Najm as it looked before the flooding of lake Tishrin

The northern entrance of the historical city of Dura Europos (Qalʿat as-Salihiyya), end of 4th century BC

The northern entrance of the historical city of Dura Europos (Qalʿat as-Salihiyya), end of 4th century BC

Krak des chevaliers (Qalʿat al-Husn), Gothic vaults

Krak des chevaliers (Qalʿat al-Husn), Gothic vaults

Exterior view of Krak des chevaliers (Qalʿat al-Husn)

Exterior view of Krak des chevaliers (Qalʿat al-Husn)

The northern entrance of the historical city of Dura Europos (Qalʿat as-Salihiyya), end of 4th century BC

The northern entrance of the historical city of Dura Europos (Qalʿat as-Salihiyya), end of 4th century BC

The gate of south-western side, Dura Europos (Qalʿat as-Salihiyya)

The gate of south-western side, Dura Europos (Qalʿat as-Salihiyya)

The northern entrance of the historical city of Dura Europos (Qalʿat as-Salihiyya), end of 4th century BC

The northern entrance of the historical city of Dura Europos (Qalʿat as-Salihiyya), end of 4th century BC

The northern entrance of the historical city of Dura Europos (Qalʿat as-Salihiyya), end of 4th century BC

The northern entrance of the historical city of Dura Europos (Qalʿat as-Salihiyya), end of 4th century BC

Excavation works, Dura Europos (Qalʿat as-Salihiyya)

Excavation works, Dura Europos (Qalʿat as-Salihiyya)

The northern entrance of the historical city of Dura Europos (Qalʿat as-Salihiyya), end of 4th century BC

The northern entrance of the historical city of Dura Europos (Qalʿat as-Salihiyya), end of 4th century BC

The northern entrance of the historical city of Dura Europos (Qalʿat as-Salihiyya), end of 4th century BC

The northern entrance of the historical city of Dura Europos (Qalʿat as-Salihiyya), end of 4th century BC

The northern entrance of the historical city of Dura Europos (Qalʿat as-Salihiyya), end of 4th century BC

The northern entrance of the historical city of Dura Europos (Qalʿat as-Salihiyya), end of 4th century BC

The Nabataean gate with its main arch, columns and capitals

The Nabataean gate with its main arch, columns and capitals

Jurn Kabir, a typical old house of the Euphrates valley near Qalʿat Najm with a large log (willow) transverse to the longitudinal axis.

Jurn Kabir, a typical old house of the Euphrates valley near Qalʿat Najm with a large log (willow) transverse to the longitudinal axis.

Excavation works, Dura Europos (Qalʿat as-Salihiyya)

Excavation works, Dura Europos (Qalʿat as-Salihiyya)

Small vaulted passageway, Qalʿat Harim

Small vaulted passageway, Qalʿat Harim

Ruins of Qalʿat ash-Shugr wa-Bakas on the edge of a mountain slope

Ruins of Qalʿat ash-Shugr wa-Bakas on the edge of a mountain slope

Part of the walls, Qalʿat Harim

Part of the walls, Qalʿat Harim

View into a vaulted room of Najm Castle (Qalʿat Najm)

View into a vaulted room of Najm Castle (Qalʿat Najm)