The temple was that of Caesarea Panias. Gerusalemme Conquistata - even much more than the Liberata - is a triumph of imagination and fantasy, but, at the same time, Tasso read whatever he could retrieve about the history of the Holy Land. Here the issue is connected to that of the element water, with which Tasso had a true obsession, as we'll see more in depth in some future.
The most interesting aspect here is the decadence, ruin, death of every human work. This is a feature Tasso profoundly shares with the ancient poem Beowulf, even if he couldn't know about it. He did know the 16th century works by Olaus Magnus, Olav Manson. Anyway, really looks like Destiny - a genuine Beowulfian concept! - wove together the threads of the Renaissance poet and of his unknown Nordic colleague. In fact, Tasso's Sophoclean/Shakespearean tragedy Il Re Torrismondo (it might be translated as King Thorismond) is set in basically the same place and time as Beowulf: Scandinavia, sixth century AD, in a "more heathen than Christian" looking society.
N.B. In the manuscript, Tasso had at first written "barbarian injuries" instead of "our," then he realized he knew better than that.