The throne is represented on the Ark of the Covenant as two Cherubim whose wings form God's "Seat of Mercy." Isaiah offers a vision in which God sits upon that throne. By contrast, Ezekiel's vision describes God upon a chariot, also supported by Cherubim. Some understand that both prophets are describing the same entity. As a result it is sometimes characterized as God's "Throne-Chariot."
There are many vivid descriptions of the Throne and its prominent features. It is a celestial sky blue, the same blue that is part of the fringes an Israelite must wear. Another Midrash calls it chashmal, amber. Made of half fire, half hail, it hovers in the air, is 800,000 parsangs in length and 500,000 in width -- and that is calculated in the parsang of heaven, which is 2000 cubits of the length of God's arm (PdRE 3, 4, 6; BHM 2:25, 41-46).
When sitting upon the Throne in judgment, God is draped in a supernal robe of purple inscribed with the names of the martyrs of Israel (Mid. Teh. 4:12). The Throne is also inscribed with the image of the patriarch Jacob (Gen. R. 68:12; PdRE 35). Thus the Throne, like God's tefillin, represents the metaphysical bond of the people Israel to the Godhead (Hechalot Zutarti).
The angel Sandalfon stands over the Throne, weaving the prayers of Israel into God's crown. Four Princes surround the Throne: Michael (right), Gabriel (left), Uriel (in front), and Raphael (behind). Other texts describe myriads of armies of angels arrayed around it. The earth is the footstool of God's throne.
There is a tradition that there are actually two thrones, the Throne of Strict Justice and the Throne of Mercy. When Israel prays for forgiveness, those supplications move God to leave the first and sit in the second (Sanh. 38b).
Despite the detailed and exacting mythic descriptions, the exact nature of the Throne is difficult to pin down. It has sentience and at times it speaks --and sings. Some passages suggest the Throne consists entirely of Cherubim and Ofanim (winged and wheeled angels) (Hechalot Rabbati).
Later Kabbalistic teachings tend to understand the Throne as being more metaphorical than actual. As a result, various sources equate the Throne with the heavens, the divine mind (Mada'ey ha-Yahadut), the supernal first light of Creation, or the Torah (Meshiv Devarim Nekhochim). Some Kabbalistic sources coyly intimate that the Throne is, like the Shekina, an attribute of the divine feminine principle, so when the Glory of God sits upon it, it signifies a hieros gamos; that the male and female principles are unified.
Based on Daniel 7:9, one Sage teaches there are thrones for the righteous that exist beside the Throne. Abraham, Moses, and David sit upon these thrones. Metatron, the "lesser YHVH" also has a throne proximate to the Throne of Glory. It is such an enthronement in the presence of God, amounting to a kind of "angelfication," that is the ultimate desire of the Merkavah mystic.
Akin to this idea that God draws the righteous close to His throne, there are a number of traditions about what God keeps under the throne, including a treasury of souls waiting to be born and a treasury of souls of the saintly dead. Four angelic encampments are arranged around the throne, just as the tribes of Israel were once arrayed around the Tabernacle while they encamped in the desert (PRE 4).
In the World-to-Come, the Throne will become visible and evident to all (P. Shabbat 6:9).