The Camp of Diocletian was a Roman military complex built in the late 3rd century AD, constructed after the destruction of Zenobia's Palmyrene Empire. It occupied the western part of the old city and included a large courtyard, a temple, a colonnaded praetorium (headquarters), and the standard grid of a Roman castra adapted to the desert terrain.
The camp survives as a scattered set of ruins within the broader Palmyra archaeological zone. The most visible element is the Temple of the Standards, a military shrine that stood at the heart of the camp. Much of this area suffered less destruction than the older Roman ruins to the east, partly because it was less monumental and less symbolically significant to ISIS.