The Mount of the Congregation in the Old Testament (Isaiah 14:13), has been supposed to refer to the place where God promised to meet with his people (Exodus 25:22; 29:42-43) i.e., the mount of the Divine presence, Mount Zion. But here the King of Babylon must be taken as expressing himself according to his own heathen notions, and not according to those of the Jews. The “mount of the congregation” will therefore in this case mean the northern mountain, supposed by the Babylonians to be the meeting-place of their gods. In the Babylonian inscriptions mention is made of a mountain which is described as “the mighty mountain of Bel, whose head rivals heaven, whose root is the holy deep.” This mountain was regarded in their mythology as the place where the gods had their seat. In Babylonian inscriptions is described as a mountain called Im-Kharasak. It is said to be mount El-wend, near Ecbatana.
This article incorporates text from a publication now in the public domain: Easton, Matthew George (1897). "article name needed". Easton's Bible Dictionary (New and revised ed.). T. Nelson and Sons.