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

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

at-Tabqa, Jaʿbar Castle, Towers of western walls

at-Tabqa, Jaʿbar Castle, Towers of western walls

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

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

At-Tabqa , Jaʿbar Castle, Bastion with loopholes.

At-Tabqa , Jaʿbar Castle, Bastion with loopholes.

Jaʿbar castle, southern side of the castle

Jaʿbar castle, southern side of the castle

A general view of the remains of Shayzar Castle

A general view of the remains of Shayzar Castle

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

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

Machicolations on the wall of Damascus Citadel

Machicolations on the wall of Damascus Citadel

Remains of Islamic Jaʿbar castle

Remains of Islamic Jaʿbar castle

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.

Jisr ash-Shughur, Qalʿat ash-Shugr wa-Bakas, the trail around the two castles

Jisr ash-Shughur, Qalʿat ash-Shugr wa-Bakas, the trail around the two castles

Jisr ash-Shughur, the ruins of Qalʿat ash-Shugr wa-Bakas, a twin crusader castle

Jisr ash-Shughur, the ruins of Qalʿat ash-Shugr wa-Bakas, a twin crusader castle

Jisr ash-Shughur, the ruins of Qalʿat ash-Shugr wa-Bakas, a twin crusader castle

Jisr ash-Shughur, the ruins of Qalʿat ash-Shugr wa-Bakas, a twin crusader castle

Qalʿat ash-Shugr wa-Bakas, the connection bridge between the two castles

Qalʿat ash-Shugr wa-Bakas, the connection bridge between the two castles

Jisr ash-Shughur, Qalʿat ash-Shugr wa-Bakas, the ruin of the twin crusader castle

Jisr ash-Shughur, Qalʿat ash-Shugr wa-Bakas, the ruin of the twin crusader castle

Tartus, Qalʿat al-Marqab, Crusader castle, general view from the Castle.

Tartus, Qalʿat al-Marqab, Crusader castle, general view from the Castle.

Jisr ash-Shughur, Qalʿat ash-Shugr wa-Bakas, a twin crusader castle, Arabic inscription

Jisr ash-Shughur, Qalʿat ash-Shugr wa-Bakas, a twin crusader castle, Arabic inscription

Jisr ash-Shughur, Qalʿat ash-Shugr wa-Bakas, a twin crusader castle, stone arch

Jisr ash-Shughur, Qalʿat ash-Shugr wa-Bakas, a twin crusader castle, stone arch

Jisr ash-Shughur, Qalʿat ash-Shugr wa-Bakas, a twin crusader castle, stone arches

Jisr ash-Shughur, Qalʿat ash-Shugr wa-Bakas, a twin crusader castle, stone arches

Jisr ash-Shughur, Qalʿat ash-Shugr wa-Bakas, a general view of the the valley around the twin castle

Jisr ash-Shughur, Qalʿat ash-Shugr wa-Bakas, a general view of the the valley around the twin castle

Tartus, Qalʿat al-Marqab, Crusader castle, a courtyard in the castle.

Tartus, Qalʿat al-Marqab, Crusader castle, a courtyard in the castle.

Jisr ash-Shughur, Qalʿat ash-Shugr wa-Bakas, a twin crusader castle, caves

Jisr ash-Shughur, Qalʿat ash-Shugr wa-Bakas, a twin crusader castle, caves

Jisr ash-Shughur, Qalʿat Shugr wa Bekas from the inside.

Jisr ash-Shughur, Qalʿat Shugr wa Bekas from the inside.

Jisr ash-Shughur, Qalʿat ash-Shugr wa-Bakas, a twin crusader castle, general view of the site

Jisr ash-Shughur, Qalʿat ash-Shugr wa-Bakas, a twin crusader castle, general view of the site

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

View on the Euphrates River from the site of Dura Europos (Qalʿat as-Salihiyya)

View on the Euphrates River from the site of 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 gate of south-western side, Dura Europos (Qalʿat as-Salihiyya)

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

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

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