The Templars, like all people of high standing in medieval society, possessed seals of office – a metal disc bearing an emblem which would imprint an insignia in to hot wax on a document. A kind of Middle Ages identity card, hologram, electronic signature.
There wasn’t a single seal covering the entire Templar Order – provincial masters had many variants. These included the familiar two knights on riding one horse, the lamb of God and the dome of a church.
But which church did that dome belong to?
It could be the Dome of the Rock which after the First Crusade and the conquest of Jerusalem was consecrated as a church becoming the Templum Domini. This was right next to the Templars HQ at what had been the Al Aqsa mosque under Muslim control but then became the Temple of Solomon under the Templars. Nearby the Augustinians also set themselves up on the Templar Mount.
But more likely, it was the Holy Sepulchre. This was the church founded by Saint Helen – the mother of the first Christian Roman emperor Constantine. On a state visit to Jerusalem in the fourth century, she miraculously discovered several key locations in the life of Jesus including his crucifixion and burial. The Holy Sepulchre church covers both these locations.
This church was epic even by late Roman standards but suffered in the seventh century AD when the Persians overran the borders of the eastern Roman (or Byzantine if you prefer) empire and torched Jerusalem including Holy Sepulchre. It was restored up to a point by the Emperor Heraclius when he re-invaded before falling under Islamic control under the same unfortunate Emperor.
Initially, the Muslims were light handed in their treatment of the Christians and the Church but under the radical Fatimid caliph Hakim – whose name even suggests a violent temperament – the place was razed to the ground. He pretty much insisted that any remains should be knee high. The dismantling of Constantine’s basilica was a massive undertaking and proved exceedingly difficult, but it was done.
Once the caliph died, the Byzantine emperor Monomachos in far off Constantinople negotiated with a new caliph in 1048 to fund the reconstruction of the church. It would never be on Constantine’s massive scale but it was pretty big. This was the church that the Templars arrived at when Jerusalem came back in to Christian control during the crusades. And it’s this church that the Templars used as a template for their places of worship and represented on their seal.
The Templars were based, as I said, in the Al Aqsa Mosque near the Dome of the Rock and built substantial annexes on the left and right hand sides of the earlier Islamic building. One of these annexes is now the women’s mosque and the other is an Islamic museum.