Just need to clarify this a bit:
The Burn was not created by repeated primal summons. It was created when the Allagans used an aetheric siphon (known today as the House of the Crooked Coin on the Azim Steppe) to cut off the circulation of aether to the region, excavated the aether-starved land, and launched it into the sky; those bits of land are what we know as Azys Lla. The siphon was never turned off after the fall of Allag, creating what came to be known as the Burn. That it was the result of repeated primal summons is simply something Solus (a.k.a. Emet-Selch) lied to the Garleans about toexcusejustify the "eternal conquest" mentality he imparted them with.
The rest is correct - Bozja Citadel was the testing site of the Lunar Transmitter, which destroyed the city and killed Midas nan Garlond. The GNB questline also reveals that it was a major Hrothgar city.